Oxidation and Deposits

Oxidation is the most important form of chemical breakdown of motor oil and its additives. The chemicals in motor oil are continuously reacting with oxygen inside an engine. The effects of oxidation, due to this reaction, as well as the by-products of combustion, produce very acidic compounds inside an engine.

The various acidic compounds cause corrosion of internal engine components, deposits, changes in oil viscosity, varnish, sludge and other insoluble oxidation products that can cause a performance and durability degradation of your engine over a period of time due to oil breakdown. The products of oxidation are less stable than the original base hydrocarbon molecular structure and, as they continue to be attacked by these acidic compounds, can produce varnish and sludge.

As an engine goes through multiple heating and cooling cycles, this sludge can harden and cause other problems such as restricted passageways and decreased component tolerances. Varnish can cause such things as piston ring and valve sticking. The deposits can also affect heat transfer from pistons to cylinder, and in extreme cases, can cause seizure of the piston in the cylinder. Pistons also have oil return slots machined into them that can become plugged and result in increased oil consumption and additional deposits created on top of the deposits that are already there, caused by oil breakdown.

Deposits also form on the tops of pistons which, over a period of time, can cause pre-ignition, increased fuel octane requirements, detonation/pinging and increased exhaust hydrocarbon emissions and an overall destructive effect on the engines internal parts. Deposits also form inside valve covers, timing gear covers, oil pump pickup screens, oil filters and oil passageways.

Part of the job of refining petroleum oil is to remove as many naturally occurring chemicals that can reduce the oxidation resistance of oil. Oxidation resistance can then be improved by the addition of additives engineered into the oil, such as anti-oxidants. Anti-oxidants include several different chemicals with the most common one being ZDDP (Zinc Diethyl Dithiophosphate). Anti-oxidants also become depleted with use and when that happens the oil starts to oxidize rapidly causing oil breakdown.

Refining an oil to reduce these naturally occurring chemicals that can lead to oxidation and oil breakdown, also, tends to inhibit the capability of oil to provide good boundary lubrication. Some of these chemicals that are refined out include aromatics, unsaturates and napthenes. Therefore, petroleum motor oil that has been highly refined using modern techniques will have good oxidation resistance but poor boundary lubrication.

Boundary lubrication can be improved and oil breakdown reduced by the use of engineered additives blended in by the oil manufacturer. This illustrates the case that refining petroleum oil is a compromise. The chemicals that come out of the ground cannot be controlled and have to be refined out. The extent of refining is usually selected to give the proper balance to meet the specifications for a particular grade of lubricant, whether it be for high performance, severe duty, average use or anywhere in between.

via Motor oil Breakdown.

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What Is Oxidation In Lubricating Oil? By MARK BARNES

Dimers of carboxylic acids are often found in ...

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When explaining what oxidation is, no one does it better than Mark Barnes from
Noria Corp. We wanted to share his input from a past issue of POA Magazine.
Oxidation is perhaps the most common chemical reaction, not just in lubrication
chemistry, but also in nature as a whole. Simply stated, oxidation is the chemical
reaction of an oil molecule with oxygen, which is present from either ambient or
entrained air. (In a strict chemical sense, oxidation does not necessarily need to
involve oxygen, although for the purposes of this article, the discussion is confined to
oxidation reactions involving oxygen.) Oil oxidation is no different than other
commonly encountered oxidation reaction, such as rusting. Just like the effects
rusting and other corrosive processes have on metal substrates, oil oxidations results
in a catastrophic and permanent chemical change to the base oil molecules.
In the case of oil oxidation, the reaction results in the sequential addition of oxygen
to the base oil molecules, to form a number of different chemicals species, including
aldehydes, ketones, hydroperoxides and carboxylic acids.
The rate at which base oil molecules react with oxygen depends on a number of
factors. Perhaps the most critical is temperature. Like many chemical reactions,
oxidation rates increase exponentially with increasing temperature due to the
Arrehenius rate rule. For most mineral oils, a general rule of thumb is that the rate of
oxidation doubles for every 10°C (18°F) rise in temperature above 75°C (165°F).
Because of this, synthetic oils are often required in high temperature applications to
prevent rapid oil oxidation. But why are synthetic hydrocarbon oils (SHCs) more
oxidatively stable than conventional minerals oils? After all, they’re both comprised
of carbon and hydrogen atoms joined together in similar paraffinic chains to refined
mineral oils.
The answer to this question is two-fold. First, SHCs, and for that matter highlyrefined
mineral oils, have very few impurities. Some of the impurities, particularly
aromatic compounds found in solvent refined mineral oils, are less stable than the
paraffinic molecules that comprise the majority of molecules in SHCs and highlyrefined
mineral oils.
The Effects of Oxidation – What to Look for on an Oil Analysis Report
While controlling temperature and using higher-quality base oils can help limit the
degree and rate of oxidation, the eventual breakdown of the base oil molecules due
to oxidative processes is inevitable. One common feature of these reaction byproducts
is the carbon-oxygen double bonds, termed a carbonyl group. Carbonyl
groups are noted for their characteristic absorption of infrared light in the 1740 cm-1
region. For this reason, Fourier transform infrared spectroscopy (FTIR), which
measures the degree of infrared absorption in different parts of the infrared
spectrum, can be an excellent tool for pinpointing base oil oxidation.
Perhaps the most noteworthy of the reaction by-products are the carboxylic acids. As
the name implies, carboxylic acids are acidic in nature, just like other more common
acids such as sulfuric and hydrochloric acids, although they are not nearly as strong.
Common household vinegar contains carboxylic acid – an acetic acid. Because oil
oxidation results in the formation of carboxylic acids, it stands to reason that the
acidity of an oil that has undergone appreciable oxidation will increase. As such, an
Acid Number test, which uses a wet chemistry titration method to determine the
concentration of acids present in an oil, can be used to determine the degree to
which an oil has oxidized.
Care must be exercised when using Acid Number data to gauge oil oxidation because
a number of additives – both new and degraded – can result in changes in an oil’s
Acid Number and can mask the real effects of base oil oxidation. Similarly,
depending on the working environment, certain ingressed contaminants may also
cause the acid number to change, masking the effects of oil oxidation. For this
reason, the presence of a characteristic infra peak at 1740 cm-1 in the FTIR
spectrum can be an instructive piece of confirmatory evidence when assessing oil
oxidation.
While carboxylic acids by themselves are bad news and can cause acidic corrosion,
an increase in acid number is usually a harbinger (forerunner) of an even more
damaging chemical process – the formation of sludge and varnish. Sludge and
varnish form when oxygenated reaction by-products, such as hydroperoxides and
carboxylic acids, combine to form larger molecular species. When a number of such
molecules combine, the process is termed polymerization and results in the
formation of large molecules of high molecular weight.
Because the viscosity of an oil is directly related to the size of the molecules, any
degree of polymerization will result in an increase in the measured viscosity. Allowed
to progress too far, polymerization continues to such an extent that solid material -
sludge and varnish – forms in the oil, as the molecules become too large to remain a
liquid. This material is sticky and can cause filter plugging, fouling of critical oil
clearances and valve stiction in hydraulics systems.

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Severe-Duty, Diesel, Turbo, SC’ed Engine Oil

Most vehicles operate under severe service as defined by vehicle manufacturers, but the majority of vehicle owners are unaware of this. Severe service applications include towing, hauling, plowing, off-road use, frequent stop-and-go driving, steep-hill driving and temperature extremes. They require different change intervals and a different type of oil. These are more robust engine oils with a HT/HS viscosity greater than 3.5 cP. They are represented by ACEA and API categories for passenger, light vans, trucks and commercial vehicles as follows:

API categories (Diesel / Gasoline): CJ-4/SM, CI-4/SL *
ACEA categories (catalist compatible): C3 , C4*
ACEA category E (Heavy Duty Diesel): E4, E6,E7,E9*
ACEA categories A/B (Gasoline/Diesel) for severe service: A3/B3, A3/B4*
(*see links on the left for more information)

Somewhat thicker oils may offer more protection for more severe operations such as driving through mountains, pulling a boat, dusty conditions, short trips, low rpm combined with high torque output per piston, overloading, overheating and over cooling. All these represent a potential danger for MOFT (minimum oil film thickness) and extra cushion in the oil film and/or high anti wear additives is recommended. MOFT is directly proportional to HTHS viscosity and RPM and inversely proportional to torque.

Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is thicker oil films can accommodate larger contaminants. Temperature has a big effect on viscosity and film thickness as motor lubricants are non-Newtonian fluids.

Be aware of your driving habits. A good rule of thumb is that for every 10 degrees Celsius you increase the temperature, you cut the oil life in half (oxidation rate doubles) and for every 10 degrees increase, you need to move up one SAE grade to keep the same viscosity.

Thicker is not better unless you thin (heat) it down. Choosing an oil too thick at operating temperature for your use and application causes efficiency loss, heat generation from internal fluid friction and possibly oil consumption from the increased effort to scraping it off the cylinder walls (at high RPMs). Low temperature flow will also be affected even if you stay within the same W(inter) grade.

If low temp and start-up protection is to be kept as recommended, it would only makes sense to decrease the winter number when choosing a heavier than recommended oil. Go down a grade in the xW- number for each SAE grade you go up. In this wide span case we strongly recommend using natural high viscosity index base stock oils (e.g. poly-alpha-olefin, polyol-ester, di-ester) since they don’t rely (greatly) on pour point depressants and polymers (viscosity index improvers) to do the job and consequently are not as shear prone.

Every fluid is a compromise. Oils recommended by the auto manufacturers seem to compromise protection from wear under severe conditions to gain fuel economy and catalyst durability. The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick.

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NA Gasoline Engine, Low Friction Oil

English: Motor oil, Mobile 1 bottle blocked out

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Thinner oils are being used these days for three reasons: they save fuel in test engines, the viscosity rules have changed because modern injection systems allow lower start-up temperatures and manufacturers (e.g. Honda, Toyota, Ford, GM, Mazda ) are recommending thinner grades. We must give credit to the OEM’s (original equipment manufacturers) who over the years have produced better and better metallurgy with tighter and tighter tolerances that go through micro-polishing processes. The better finishing of parts has allowed for better lubrication even at a lower viscosity such as SAE 5W-20 or 0W-20 helping with pumping and winding losses without sacrificing robustness and HTHS (high temperature high shear) viscosity as much.

As far as energy conserving 30 weight multigrades go, a big factor in fuel economy is temporary polymer shear. These polymers are additives known as viscosity index improvers (or modifiers) but also pour point depressants. Polymers are plastics dissolved in oil to provide multi-viscosity characteristics.
As oil is forced between a bearing and journal, many polymers have a tendency to align with each other. When this happens, viscosity drops. Then when the oil progresses through the bearing, the polymer molecules entangle again and viscosity returns to normal. This phenomenon is referred to as temporary shear and is measured by the HTHS test.
Oil formulators rely on (temporary) polymer shear to pass the fuel economy test for resource conserving xW-30 multigrade oils. The HTHS viscosity is therefore a lower number (compared to other more robust 30 weights).
HTHS viscosity has become the single, most important measure of motor oil and you can tell how much an oil has wear protection and fuel economy from the HTHS viscosity alone. Note that most modern gasoline engines don’t require too high HTHS viscosity to protect against wear and you can benefit from fuel economy of small HTHS viscosities without causing significantly more wear than with larger HTHS viscosites (in normal driving conditions).

High quality and very polar friction modifiers like organic molybdenum and boron or certain esters also play a big part in fuel economy. High levels of friction modifiers may negatively impact the performance of detergents and dispersants since they all compete on the same (limited) surface. Just the reason why HDEO’s are wet clutch compatible and also make for a good slow acting/safe engine flush/cleaner.

We think that these oils represent a very careful compromise between fuel economy vs. protection and long drain intervals vs. slipperiness/lubricity. A motor oil is only as good as its weakest link. Balance is of the essence in this case !
Formulating wear resistant thin oils is a challenging task for the manufacturers especially now when the best last resort protection mix -zinc, phosphorus (anti-ware additives) and moly (extreme-pressure additive)- is lower and lower. A good abrasion resistance can be obtained as long as most of the (high) shear resistance is based on a high quality base oil (e.g. POE, PAO) and not on polymer viscosity improvers.

Besides the fuel economy and minimum power losses, these high quality oils offer very good start-up viscosity and good pumping and flow attributes helping with the growing conscience of start-up wear and arctic capable injection systems. They reduce warm-up time transferring heat better but also reduce operational temperatures over thicker oils acting as a better coolant (lower internal friction).

The ACEA defines a Fuel Economy lubricant as a lubricant in compliance with ACEA C1, C2, A5/B5, A1/B1 standards (C-catalyst compatible, A-gasoline engines, B-Diesel).
The API and ILSAC following categories apply to 0,5,10W(winter) multigrades – for gasoline engines only : API SN – RESOURCE CONSERVING and ILSAC GF-5.

These lubricants are mostly suited for service of late model naturally aspirated gasoline engines (low torque@low RPM/cylinder) that are built with tight clearances. (e.g. USDM, JDM)

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ESTERS IN SYNTHETIC LUBRICANTS By T. G. Schaefer

Ethyl lactate (Chemical Structure)

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In the simplest terms, esters can be defined as the reaction products of acids and alcohols. Thousands of different kinds of esters are commercially produced for a broad range of applications. Within the realm of synthetic lubrication, a relatively small but still substantial family of esters have been found to be very useful in severe environment applications. This paper shall provide a general overview of the more common esters used in synthetic lubricants and discuss their important benefits and utilities.

Esters have been used successfully in lubrication for more than 60 years and are the preferred stock in many severe applications where their benefits solve problems or bring value. For example, esters have been used exclusively in jet engine lubricants worldwide for over 50 years due to their unique combination of low temperature flowability with clean high temperature operation. Esters are also the preferred stock in the new synthetic refrigeration lubricants used with CFC replacement refrigerants. Here the combination of branching and polarity make the esters miscible with the HFC refrigerants and improves both low and high temperature performance characteristics. In automotive applications, the first qualified synthetic crankcase motor oils were based entirely on ester formulations and these products were quite successful when properly formulated. Esters have given way to PAOs in this application due to PAOs lower cost and their formulating similarities to mineral oil. Nevertheless, esters are often used in combination with PAOs in full synthetic motor oils in order to balance the effect on seals, solubilize additives, reduce volatility, and improve energy efficiency through higher lubricity. The percentage of ester used can vary anywhere from 5 to 25% depending upon the desired properties and the type of ester employed.

The new frontier for esters is the industrial marketplace where the number of products, applications, and operating conditions is enormous. In many cases, the very same equipment which operates satisfactorily on mineral oil in one plant could benefit greatly from the use of an ester lubricant in another plant where the equipment is operated under more severe conditions. This is a marketplace where old problems or new challenges can arise at any time or any location. The high performance properties and custom design versatility of esters is ideally suited to solve these problems. Ester lubricants have already captured certain niches in the industrial market such as reciprocating air compressors and high temperature industrial oven chain lubricants. When one focuses on temperature extremes and their telltale signs such as smoking and deposits, the potential applications for the problem solving ester lubricants are
virtually endless.

Ester Chemistry

In many ways esters are very similar to the more commonly known and used synthetic hydrocarbons or PAOs. Like PAOs, esters are synthesized from relatively pure and simple starting materials to produce predetermined molecular structures designed specifically for high performance lubrication. Both types of synthetic basestocks are primarily branched hydrocarbons which are thermally stable, have high viscosity indices, and lack the undesirable and unstable impurities found in conventional petroleum based oils. The primary structural difference between esters and PAOs is the presence of multiple ester linkages (COOR) in esters which impart polarity to the molecules. This polarity affects the way esters behave as lubricants in the following ways:

1) Volatility: The polarity of the ester molecules causes them to be attracted to one another and this intermolecular attraction requires more energy (heat) for the esters to transfer from a liquid to a gaseous state. Therefore, at a given molecular weight or viscosity, the esters will exhibit a lower vapor pressure which translates into a higher flash point and a lower rate of evaporation for the lubricant. Generally speaking, the more ester linkages in a specific ester, the higher its flash point and the lower its volatility.

2) Lubricity: Polarity also causes the ester molecules to be attracted to positively charged metal surfaces. As a result, the molecules tend to line up on the metal surface creating a film which requires additional energy (load) to wipe them off. The result is a stronger film which translates into higher lubricity and lower energy consumption in lubricant applications.

3) Detergency/Dispersency: The polar nature of esters also makes them good solvents and dispersants. This allows the esters to solubilize or disperse oil degradation by-products which might otherwise be deposited as varnish or sludge, and translates into cleaner operation and improved additive solubility in the final lubricant.

4) Biodegradability: While stable against oxidative and thermal breakdown, the ester linkage provides a vulnerable site for microbes to begin their work of biodegrading the ester molecule. This translates into very high biodegradability rates for ester lubricants and allows more environmentally friendly products to be formulated.

Another important difference between esters and PAOs is the incredible versatility in the design of ester molecules due to the high number of commercially available acids and alcohols from which to choose. For example, if one is seeking a 6 cSt synthetic basestock, the choices available with PAOs are a straight cut 6 cSt or a “dumbbell” blend of a lighter and heavier PAO. In either case, the properties of the resulting basestock are essentially the same. With esters, literally dozens of 6 cSt products can be designed each with a different chemical structure selected for the specific desired property. This allows the “ester engineer” to custom design the structure of the ester molecules to an optimized set of properties determined by the end customer or application. The performance properties that can be varied in ester design include viscosity, viscosity index, volatility, high temperature coking tendencies, biodegradability, lubricity, hydrolytic stability, additive solubility, and seal compatibility.

As with any product, there are also downsides to esters. The most common concern when formulating with ester basestocks is compatibility with the elastomer material used in the seals. All esters will tend to swell and soften most elastomer seals however, the degree to which they do so can be controlled through proper selection. When seal swell is desirable, such as in balancing the seal shrinkage and hardening characteristics of PAOs, more polar esters should be used such as those with lower molecular weight and/or higher number of ester linkages. When used as the exclusive basestock, the ester should be designed for compatibility with seals or the seals should be changed to those types which are more compatible with esters.

Another potential disadvantage with esters is their ability to react with water or hydrolyze under certain conditions. Generally this hydrolysis reaction requires the presence of water and heat with a relatively strong acid or base to catalyze the reaction. Since esters are usually used in very high temperature applications, high amounts of water are usually not present and hydrolysis is rarely a problem in actual use. Where the application environment may lead to hydrolysis, the ester structure can be altered to greatly improve its hydrolytic stability and additives can be selected to minimize any effects.

The following is a discussion of the structures and features of the more common ester families used in synthetic lubrication.

Diesters

Diesters were the original ester structures introduced to synthetic lubricants during the second World War. These products are made by reacting monohydric alcohols with dibasic acids creating a molecule which may be linear, branched, or aromatic and with two ester groups. Diesters which are often abbreviated DBE (dibasic acid esters) are named after the type of dibasic acid used and are often abbreviated with letters. For example, a diester made by reacting isodecyl alcohol with adipic acid would be known as an “adipate” type diester and would be abbreviated “DIDA” (Diisodecyl Adipate).

Adipates are the most widely used diesters due to their low relative cost and good balance of properties. They generally range from about 2.3 to 5.3 cSt at 100°C and exhibit pour points below -60°C. The viscosity indices of adipates usually run from about 130 to 150 and their oxidative stability, like most of the diesters, are comparable to PAOs. The primary difference between adipate diesters and PAOs is the presence of two ester linkages and the associated polarity benefits outlined previously. The most common use of adipate diesters is in combination with PAOs in numerous applications such as screw compressor oils, gear and transmission oils, automotive crankcase oils, and hydraulic fluids. Adipates are also used as the sole basestock where biodegradability is desired or high temperature cleanliness is critical such as in textile lubricants and oven chain oils.

Azelates, sebacates, and dodecanedioates are similar to adipates except that in each case the carbon chain length (backbone) of the dibasic acid is longer. This “backbone stretching” significantly increases viscosity index and improves the lubricity characteristics of the ester while retaining all the desirable properties of the adipates. The only downside to these types of diesters is price which tends to run about 50 – 100+% higher than adipates at the wholesale level. This group of linear DBEs are mainly used in older military specifications and where the lubricity factor becomes an important parameter.

Phthalates are aromatic diesters and this ring structure greatly reduces the viscosity index (usually well below 100) and eliminates most of the biodegradability benefit. In all other respects, phthalates behave similar to other diesters and are about 20 – 30% lower in cost. Phthalates are used extensively in air compressor lubricants (especially the reciprocating type) where low viscosity index is the norm and low cost clean operation is desirable.

Dimer acid is made by combining two oleic acids which creates a large branched dibasic acid from which interesting diesters are made. Dimerates exhibit high viscosity and high viscosity indices while retaining excellent low temperature flow. Compared to adipates, dimerates are higher in price (30 – 40%), have marginal biodegradability, and are not as clean in high temperature operations. Their lubricity is good and they are often used in synthetic gear oils and 2-cycle oils.

The alcohols used to make diesters will also affect the properties of the finished esters and thus are important factors in the design process. The alcohols may be reacted alone or blended with other alcohols to form coesters with their own unique properties. The first three alcohols in the table above all contain eight carbons, and when reacted with adipic acid, all create a dioctyl adipate. However, the properties are entirely different. The n-octyl adipate would have the highest viscosity and the highest viscosity index (about 50% higher then the 2-ethylhexyl adipate) but would exhibit a relatively high freeze point making their use in low temperature applications virtually impossible. By branching the octyl alcohol, the other two DOAs exhibit no freeze point tendencies and have pour points well below -60°C. The isooctyl adipate offers the best balance of properties combining a high viscosity index with a wide temperature range. The 2-ethylhexyl adipate has a VI about 45 units lower and a somewhat higher volatility. These examples demonstrate the importance of combining the right alcohols with the right acids when designing diester structures and allows the ester engineer a great deal of flexibility in his work.

Polyol esters

The term “polyol esters” is short for neopentyl polyol esters which are made by reacting monobasic acids with polyhedric alcohols having a neopentyl structure. The unique feature of the structure of polyol ester molecules is the fact that there are no hydrogens on the beta-carbon. Since this “beta-hydrogen” is the first site of thermal attack on diesters, eliminating this site substantially elevates the thermal stability of polyol esters and allows them to be used at much higher temperatures. In addition, polyol esters usually have more ester groups than the diesters and this added polarity further reduces volatility and enhances the lubricity characteristics while retaining all the other desirable properties inherent with diesters. This makes polyol esters ideally suited for the higher temperature applications where the performance of diesters and PAOs begin to fade.

Like diesters, many different acids and alcohols are available for manufacturing polyol esters and indeed an even greater number of permutations are possible due to the multiple ester linkages. Unlike diesters, polyol esters (POEs) are named after the alcohol instead of the acid and the acids are often represented by their carbon chain length. For example, a polyol ester made by reacting a mixture of nC8 and nC10 fatty acids with trimethylolpropane would be referred to as a “TMP” ester and represented as TMP C8C10.

Each of the alcohols shown above have no beta-hydrogens and differ primarily in the number of hydroxyl groups they contain for reaction with the fatty acids. The difference in ester properties as they relate to the alcohols are primarily those related to molecular weight such as viscosity, pour point, flash point, and volatility. The versatility in designing these fluids is primarily related to the selection and mix of the acids esterified onto the alcohols.

The normal or linear acids all contribute similar performance properties with the physicals being influenced by their carbon chain length or molecular weight. For example, lighter acids such as valeric may be desirable for reducing low temperature viscosity on the higher alcohols, or the same purpose can be achieved by esterifying longer acids onto the shorter alcohols. While the properties of the normal acids are mainly related to the chain length, there are some more subtle differences among them which can allow the formulator to vary such properties as thermal stability and lubricity.

Branched acids add a new dimension since the length, location, and number of branches all impact the performance of the final ester. For example, a branch incorporated near the acid group may help to hinder hydrolysis while multiple branches may be useful for building viscosity, improving low temperature flow, and enhancing thermal stability and cleanliness. The versatility of this family is best understood when one considers that multiple acids are usually co-esterified with the polyol alcohol allowing the ester engineer to control multiple properties in a single ester. Indeed single acids are rarely used in polyol esters because of the enchanced properties that can be obtained through co-esterification.

Polyol esters can extend the high temperature operating range of a lubricant by as much as 50 – 100°C due to their superior stability and low volatility. They are also renowned for their film strength and increased lubricity which is useful in reducing energy consumption in many applications. The only downside of polyol esters compared to diesters is their higher price tag, generally 20 – 70+% higher on a wholesale basis.

The major application for polyol esters is jet engine lubricants where they have been used exclusively for more than 40 years. In this application, the oil is expected to flow at -65°C, pump readily at -40°C, and withstand sump temperature over 200°C with drain intervals measured in years. Only polyol esters have been found to satisfy this demanding application and incorporating even small amounts of diesters or PAOs will cause the lubricant to fail vital specifications.

Polyol esters are also the ester of choice for blending with PAOs in passenger car motor oils. This change from lower cost diesters to polyols was driven primarily by the need for reduced fuel consumption and lower volatility in modern specifications. They are sometimes used in 2-cycle oils as well for the same reasons.

In industrial markets polyol esters are used extensively in synthetic refrigeration lubricants due to their miscibility with non-chlorine refrigerants. They are also widely used in very high temperature operations such as industrial oven chains, tenter frames, stationary turbine engines, high temperature grease, fire resistant transformer coolants, fire resistant hydraulic fluids, and textile lubricants.

In general, polyol esters represent the highest performance level available for high temperature applications at a reasonable price. Although they cost more than many other types of synthetics, the benefits often combine to make this chemistry the most cost effective in severe environment applications. The primary benefits include extended life, higher temperature operation, reduced maintenance and downtime, lower energy consumption, reduced smoke and disposal, and biodegradability.

Other esters

While diesters and polyol esters represent the most widely used ester families in synthetic lubrication, two other families are worth mentioning. These are monoesters and trimellitates.

Monoesters are made by reacting monohydric alcohols with monobasic fatty acids creating a molecule with a single ester linkage and linear or branched alkyl groups. These products are generally very low in viscosity (usually under 2 cSt at 100°C) and exhibit extremely low pour points and high VIs. The presence of the ester linkage imparts polarity which helps to offset the high volatility expected with such small molecules. Hence, when compared to a hydrocarbon of equal molecular weight, a monoester will have a significantly higher flash point giving it a broader temperature range in use. Monoesters are used primarily for extremely cold applications such as in Arctic hydraulic oils and deep sea drilling. They can also be used in formulating automotive aftermarket additives to improve cold starting.

Trimellitates are aromatic triesters which are similar to the phthalates described under diesters but with a third ester linkage. By taking on three alcohols, the trimellitates are significantly more viscous then the linear adipates or phthalates. Viscosities range from about 9 to 20 cSt at 100°C. Like phthalates, trimellitates have a low viscosity index and poor biodegradability with a price range between adipates and polyols. Trimellitates are generally used where high viscosity is needed as in gear lubricants, chain lubricants, and grease.

Summary

Esters are a broad and diverse family of synthetic lubricant basestocks which can be custom designed to meet specific physical and performance properties. The inherent polarity of esters improves their performance in lubrication by reducing volatility, increasing lubricity, providing cleaner operation, and making the products biodegradable. A wide range of available raw materials allow an ester designer the ability to optimize a product over a wide range of variables in order to maximize the performance and value to the client. They may be used alone in very high temperature applications for optimum performance or blended with PAOs or other synthetic basestocks where their complementary properties improve the balance of the finished lubricant. Esters have been used in synthetic lubricants for more than 60 years and continue to grow as the drive for efficiency make operating environments more severe. Because of the complexity involved in the designing, selecting, and blending of an ester basestock, the choice of the optimum ester should be left to a qualified ester engineer who can better balance the desired properties.

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Sneak-Peak at Some of the Top Chevys of All Time

Sneak-Peak at Some of the Top Chevys of All Time

Chevrolet turned 100 last month, and in observance of the impact the company has had on America we’re taking the opportunity to note some of the best Chevys ever to roll off the assembly line. These vehicles were selected by Super Chevy Magazine as some of the most influential models of the past 100 years, but you’ll have to pick up the magazine to see how they ranked. Super Chevy is the largest title dedicated to the performance car brand, testament to Chevrolet’s long history and loyal following of enthusiasts.

You can view the entire list of 100 greatest Chevys in the Special Collector’s Edition of Super Chevy Platinum Magazine, but for now here are a few examples of why Chevy is still a beloved American icon. See a few of the Top 100 below.

1911 Chevrolet

Cost new: $2,150

Photo copyright GM

The first Chevrolet to hit the market touched off what was to be the beginning of an American Revolution. It featured a 299ci “T-Head” six-cylinder engine with dual camshafts and rating of 40 horsepower at a cost of $2,150.

‘56 Chevy

Cost new: $2,500

The ad tagline for the ’56 Chevy told the world ‘The Hot One’s Even Hotter’ just a year after the legendary ’55 Chevy made its impact. Featuring a Super Turbo-Fire, four-barrel 265 engine that produced 205 horsepower, Chevy launched another ad telling the public that ‘Nothing without wings climbs like a 1956 Chevrolet! Aim this new Chevrolet up a steep grade and you will see why it’s the Pikes Peak record holder.” Indeed.

’59 Chevy with Fuel Injection

Cost new: $2,500

In the last year Chevy owners could purchase a Rochester fuel-injected small-block in anything except a Corvette, this stylish automobile proved hard to find with factory fuel-injection even then. Buyers had two options, either a 250 horsepower with a hydraulic cam or 290 HP with a solid cam.

’63 Corvette Split Window

Cost new: $4,037

One of the rarest collector cars ever to be seen, the ’63 Corvette became an instant classic after safety concerns caused the rear-window design to be scrapped the following year. With a 327ci/360 hp engine, this sleek roadster is hailed as one of the finest in the history of the Corvette.

’67 Z28

Cost new: $3,500

Built with a 302ci engine/290hp for the SCCA’s Trans-Am series, the Z28 was one of the first ponycars designed to go around corners. Through virtually no advertising and little public awareness, the Z28 muscle car spurred competing models from the big players in the industry. When put to the test, it became known as the epitome of what a race car should be.

First-Gen Monte Carlo SS 454

Cost new: $3,123

Produced only in 1970 and 1971, the First-Gen Monte Carlo was a blend of Chevelle and Cadillac Eldorado that came to be known as the gentleman’s muscle car. The 360-HP big-block engine produced big speed but also provided a comfortable cruise.

’75 Caprice Classic Convertible

Cost new: $5,113

1975 was the last year consumers could purchase a full-size Chevy convertible, and the Caprice was considered a leader in luxury vehicles of the era. A 350ci/145 horsepower engine came standard, but buyers could upgrade up to 454ci/215 hp if they so desired.

C4 ZR-1

Cost new: $58,995

Evidenced by its ability to go from 0-60 in 4.4 seconds, the C4 ZR-1 was engineered to run with the best of them. In the early 90’s Lotus joined Chevy in designing the LT5 all-aluminum small-block featuring duel-overhead cams, 32 valves and 16 fuel injectors that turned out a top-speed of 180 mph.

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AMSOIL – Signature Series 100% Synthetic 0W-30 Motor Oil (AZO)

AMSOIL Signature Series Synthetic Motor Oil delivers extraordinary lubrication in all types of automotive gasoline engines. By combining industry-premier synthetic technology with AMSOIL premium additives, Signature Series Synthetic Motor Oil exceeds the higher performance demands of modern engines. It withstands the stress of higher horsepower, higher heat and complicated emissions control systems. Signature Series Synthetic Motor Oil is engineered to outperform competitive conventional and synthetic motor oils. It delivers long-lasting performance and protection.

AMSOIL, the leader in automotive synthetic lubrication, produced the world’s first API-qualified synthetic motor oil in 1972. Trust the extensive experience of AMSOIL, the First in Synthetics®, to do the best job protecting your engine.

Extends Drain Intervals

AMSOIL Signature Series Synthetic Motor Oil can extend drain intervals far beyond those recommended for conventional oils. Its unique synthetic formulation and long-drain additive system are inherently stable to resist oxidation and neutralize acids over longer periods. Signature Series Synthetic Motor Oil is designed to deliver the best possible engine protection, cleanliness and performance over extended drain intervals. It reduces vehicle

via AMSOIL – Signature Series 100% Synthetic 0W-30 Motor Oil (AZO).

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