Education and experience. Actual measurements are done by others with the means to do so.

This is Rotella country and there are still conflicting views on which variety to use. Once a viscosity range is chosen there are many excellent oils available.
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Go to bobistheoilguy.com and learn more than you ever wanted to about oil.

The physical cleanliness of the engine is one important indicator, but there are others. The main way to evaluate an oil is to have an analysis done, both before and after use. The analysis before use (called a virgin oil analysis or VOA) is usually done by someone else and posted on the web for all to reference. In some cases, it can also be used to determine if an oil is right for your vehicle. The used oil analysis (UOA) will tell you how many miles a particular oil should be used with your vehicle.

Like stated above, in vehicles with older style flat-tappet camshafts (like our trucks), diesel oil is required to prevent premature top end wear. Or you could use a standard oil and a ZDDP additive.

 

Did you have your own oil analyses done? If so please report results of before/after to answer question.
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Yes, I've had analyses run on oil from three different vehicles, and had a VOA run on an Amsoil product I was experimenting with. Other VOA were not necessary because others had posted them at BITOG. And no I won't post my analysis results simply because I don't have anything to prove or care what your opinions are.

 

This is a great thread. Lots of side by side weight tests showing oil pressure improvements. Filter cross references etc:
https://landroverforums.com/forum/di...estions-46975/