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Oxidation Stability in PC-11 Oils: A Critical Factor in Oil Performance and Engine Life

September 02, 2016


In our last PC-11 related blog, we outlined the three key traits to look for in the new engine oil categories coming out of the PC-11 initiative, API CK-4 and FA-4. Now, let’s zero in on one of those traits, which is getting a lot of attention these days: oxidation stability.

In general, an engine oil has two main functions: 1) to protect the engine, and 2) to protect itself from breaking down. High levels of oxidation drive a higher propensity for oil to break down, thicken in viscosity, form deposits and even cause corrosion of certain engine parts, which could lead to premature engine failure.


Extending Oil Drain Through Better Oxidation

In fact, oxidation is the primary reason oil has to be changed as often as it does today. Modern engines do not produce as much soot or sulfuric acids as they did 15 years ago, meaning oils are less likely to degrade due to soot accumulation or total base number (TBN) depletion. The greater risk for breakdown today is prolonged high temperature exposure causing higher oxidation. The new API CK-4 and FA-4 oils are required to improve in oxidation control over previous categories.

The new Volvo T-13 test focuses exclusively on oxidation control in the new API categories. It measures oxidation levels and viscosity change in oils exposed to temperatures up to 130o centigrade over 360 hours, pushing the oil to the very limits of what is practical. In reality, an oil is not likely to experience that level of heat, though it may for short bursts of time. Additives are required to balance the effects of oxidation and reduce the risk of breakdown. You can compare oil breakdown to food spoilage, which also is caused by oxidation and additives are used to mitigate the process.


A Change for the Better

What we are seeing is that the new oils are definitely more robust in high-temperature operation compared to today’s products. With a much lower propensity to break down, engine manufacturers may well be compelled to extend their drain interval recommendations for API CK-4 and FA-4 oils.

These benefits are relevant to both on- and off-highway applications, perhaps even more so for off-highway, where equipment often operates at higher temperatures under severe duty conditions. In either case, the combination of longer drain intervals and lower risk of engine failure should help drive lower operating costs and a greater return on investment in equipment – the bottom-line reasons for choosing any motor oil.

With Delo products, our goal is to achieve “flatline” performance in various tests, meaning that the viscosity of a used oil that has had prolonged high-temperature exposure is not much different from that of a fresh oil. For more information, please visit:


NOTE: This is the second part of a 4-part series focusing on the key traits to look for in CK-4 and FA-4 oils.