MOTOR Magazine

A MOTOR Magazine Newsletter
Oct. 23, 2018

Contributed by Bob Chabot
Is Your Auto Oil Good Enough?

Newer automobile gasoline engines need better oil

As gasoline remains the biggest fuel source for vehicles, an increasing number of new gas engines require better lubricants that last longer than the types many oil manufacturers in America currently produce. Engine operators need to maximize the return on their investment, but the availability of accurate knowledge, let alone applying it, makes this endeavor difficult.

The problem is complicated by widespread marketing. The advertising of relatively cheaper motor oils, often used for thousands more miles, dwarfs the quality of some engine-specific lubricants now being recommended by automakers. Motorists risk sacrificing the longer duration of their vehicle engines by using lower quality oils, often over long miles between changes. Typically, courts haven’t held them responsible. But for service professionals, whether you’re aware and/or advising your customers accordingly or not is another matter. Even lubricant manufacturers are beginning to look more closely at the quality and operation of their products.

Oil Degradation Tracked More Closely
Many engine manufacturers have redesigned their products. For example, one change is a focus on increasing the engine’s efficiency and power output while reducing emissions, such as NOx, according to Infineum International Ltd. Not only are the combustion temperatures and pressures higher, but also piston design changes put the top ring closer to the combustion zone. This means the lubricant used must handle higher temperatures, raising the concern of deposit formation, which may lead to ring sticking and engine damage.

To address these issues, Infineum has been using a wide range of tests to gain a deep understanding of the underlying chemistry of the lubricant and its operating environment. This work has led the company to conclude that the deposits found in modern gas engines are different from those found in older generations of engines and therefore require new formulation approaches to provide the required level of oil performance.

“In high-temperature gas engines, carbonaceous deposits occur in many different forms and locations – for example, ring-groove deposits and rocker cover sludge,” Infineum recently published. “It is essential for lubricants to either prevent deposits from forming or to stop them building up on engine surfaces. Increasing the thermal stability of the lubricant to slow its degradation is one method used to prevent deposit formation.”

“However, in the high temperatures and pressures encountered in the latest gas engines, the lubricant will eventually degrade and produce deposits. When this occurs, oils formulated with the correct balance of dispersants and detergents along with other additives can keep the deposits in solution, preventing their build-up on engine parts. Formulators must be confident that, as oil drain intervals are extended, this does not lead to excessive deposit buildup as the oil ages.”

According to Infineum, current formulations struggle to meet the lubrication challenges of new gas engines. (Image — Infineum International Ltd.)

Understanding Deposits for Improved Appliance
To effectively formulate against deposit build up, Infineum has been using a number of techniques to study the chemical and physical nature of the deposits found in natural gas engines. For example, transmission electron microscopy (TEM) revealed that deposits found in engine oils were similar in size and morphology, irrespective of from where in the engine they were collected. Approximately 90 percent of the particles, which in appearance and size were comparable to those found in diesel engines, fell within a range of 11–36 nm.

Despite these similarities, Infineum noted the particles are not formed in the same way. Heavy-duty diesel (HDD) soot is formed from incomplete combustion of fuel, while in a lean-burn gas engine operating on gasoline, it is comprised primarily of methane. With a significant amount of oxygen, the level of incomplete combustion is likely to be negligible. It is much more likely that carbonaceous deposits in gas engines result from the incomplete combustion of lubricant present in the combustion chamber.

“While the particles viewed by TEM all appeared similar, this does not preclude deposits with a different final structure forming in different parts of the engine,” Infineum published. “Scanning electron microscope (SEM) analysis revealed different topographies dependent upon the location of the deposit in the engine. Those from the rocker cover formed stacked lamella-like layers whereas those isolated from the engine oil and filter formed amorphous particles in the micron-size range.”

“As well as size and shape, the way dispersant additives interact with deposits, and ultimately their effectiveness at maintaining engine cleanliness, is dependent on the elemental and surface chemical composition of the deposits themselves. Energy-dispersive X-ray (EDX) analysis of deposits from the oil filters showed that the gas engine deposits had a much higher oxygen-to-carbon ratio than HDD soot. In addition, the gas engine deposits contained higher concentrations of calcium, zinc, phosphorous and sulfur, the presence of which could be attributed to lubricant additives.”

These results further support the view that the deposits are formed from combustion of the lubricant rather than any fuel contribution. Further spectrographic analysis revealed that when compared to HDD soot, a much lower proportion of the carbon atoms present in NGEO deposits were graphite in nature. This could be one reason that NGEO deposits may be more difficult to disperse effectively, since there are fewer graphite sheets to which the lone electron pairs in the head of the dispersant can bind.

Despite the similarities in size and shape to HDD soot (certainly when initially formed), there are clear differences in the elemental and chemical composition of the deposits found in a modern gas engine. These new deposits, which have the features of both soot and sludge, are the key reason that new and novel formulation approaches are now required.

Infineum concluded that going forward, it is now absolutely essential to choose the correct additive chemistry and base oil combination. This formulation should be based on deposit type and the knowledge of the behavior of the deposit to ensure effective cleanliness is provided over longer drain intervals for the very latest engines. For service professionals, how you approach recommending oil to your clients may be about to change.

[Editor's note: Visit for the latest diagnostic and service insights.]

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