Originally Posted By: buster
At the end of the day it's the FINAL performance that counts, including OEM and industry specifications. Whether you use Grp III/IV/V base oils, you can make a good or bad oil. It's up to the chemists and what they are shooting for. $$ is obviously a variable. There are many ways to add solvency to an oil.
Theoretically, a full ester/pao based oil should be superior, but it's all relative to what you are trying to achieve. You also have to consider the additive system. It's all about taking many complex components and making a final product. How you get there isn't necessarily that important as long as the end result is what you want.
Cost obviously will always be a factor. Grp III's are less expensive. PAO's are being used more as a correction fluid. Various esters and modern additives are used for increased solvency, wear protection etc.
Very well put Buster, and spot on!
Group IIIs have better solvency than PAOs because their cycloalkane content contributes polarity. This is why Group III based oils generally do not require esters to solubilize additives and balance seals, as PAOs do. PAOs are utterly paraffinic and, while somewhat more oxidatively stable than most Group IIIs, have poor solvency properties and tend to shrink/harden seals.
Of the common base oils, POEs have the greatest solvency characteristics, followed by ANs, Group I, Group II, Group III, and PAOs.
That said, I'll repeat what I said here in the past: "Trying to characterize the performance of a motor oil strictly by its base oil composition is an entertaining but academic game."
Tom NJ
