[Huskymaniac]

Originally Posted by icingdeath88

I just barely switched over to the Shell Rotella T6 5w40 because I noticed it was recommended/used many times by the STi/WRX guys over at Nasioc.

Do you know their reasoning? Is it to avoid viscosity breakdown due to shearing? If so, there are other options with high HTHS values. The thing that worries me about Rotella 5W40 along with most other diesel oils is that they don't contain any Molybdenum. Moly can be bad for some diesel engines. Chevron indicates that this is because Moly is a lubricant booster and OTR diesel engines with roller cam followers require a certain amount of traction for proper operation. Cummins has issued a Technical Bulletin warning against the use of moly. They apparently have documented premature cam damage in engines using an older moly additive (MDS).

But for gasoline engines, Molybdenum Disulfide is very beneficial and many racing oils (Redline) are loaded with the stuff. This is from bobistheoilguy.com:

"Molybdenum Disulfide (Moly) has been used for decades in lubricating pastes and greases because it is slippery and forms a protective coating on metal parts. Moly exists as microscopic hexagonal crystal platelets Several molecules make up one of these platelets. A single molecule of Moly contains two sulfur atoms and one molybdenum atom. Moly platelets are attracted to metal surfaces. This attraction and the force of moving engine parts rubbing across one another provide the necessary thermochemical reaction necessary for Moly to form an overlapping protective coating like armor on all of your engine parts. This protective armor coating has a number of properties that are very beneficial for your engine.

The Moly platelets that make up the protective layers on your engine surfaces slide across one another very easily. Instead of metal rubbing against metal, you have Moly platelets moving across one another protecting and lubricating the metal engine parts.

This coating effectively fills in the microscopic pores that cover the surface of all engine parts, making them smoother. This feature is important in providing an effective seal on the combustion chamber. By filling in the craters and pores Moly improves this seal allowing for more efficient combustion and engine performance.

This overlapping coating of Moly also gives protection against loading (perpendicular) forces. These forces occur on the bearings, and lifters. The high pressures that occur between these moving parts tend to squeeze normal lubricants out."

The plating action of Moly reduces friction which reduces heat. This helps keep rings free from carbon buildup, prevents blow-by, decreases emission, and extends oil life.

If it weren't for the impact of moly, I would go with Redline 5W40 oil for the same reason as these guys are going with Rotella. It doesn't break down at high temperature, high shear conditions. Redline has even more base material for even longer life than Rotella. It is like Rotella on steroids. BUT, it is also intended for diesel engines and is the ONLY Redline oil with zero moly. Now, one can buy moly oil additives. Adding this to Rotella or other diesel oils may work just fine. But that is an added expense and you never know if the oil chemistry is balanced.