What is the best oil to use?

I bought my truck new and its only had Royal Purple. Im about to change front and rear diff and engine oil but I dont want to keep paying RP if someone knows what is the best.

 

Best is subjective:

Royal Purple is pretty good stuff.
Mobil1 is good stuff.

Use what you want-

 

x2.

i have mobil 1

 

Any quality synthetic will do. Change regularly. Royal Purple is fine if you want to stick with that. Mobil 1 is also fine and a little less expensive.

If you want to do extended OCIs, stick with one brand for a few changes and get oil analyses done to determine what your OCI should be.

FWIW I ran Mobil 1 for the first 3k miles and swapped to RP a couple days ago. Plan to run RP from now on because the UOAs over at bobistheoilguy.com show it shearing down to about a 20 weight over time while still protecting excellently against engine wear.

The Diffs/T-case are still full of Mobil 1...nowhere near the needed time/mileage for a change yet...

 

I'll be putting Redline MT90 in my trans pretty soon, and M1 in everything else (5-30 in engine, 75-90 in diffs and tcase)

 

Reason for concern is I saw one article on how RP needed to change their advertising because a lot of claims were false. However I like it, I trust it will see how long my engine lasts with it.

 

Which article, exactly?

Never mind. Googled it up. Interesting. I'll still take the oil analyses.

 

This article but I haven't done too much research on it.

http://www.qldstreetscene.com/forums/index.php?showtopic=18022

 

i use rotella t 10w30. i know i know crazy but it has zinc that helps with repair of cylinder walls and also stays cooler due to it being a diesle oil. it also last a little longer and doesnt thin out as much when it does get hot. look into it. i have been running it in my truck for about a year now.

 

Yeah I saw it.

Before switching to RP I went over to the Bob forums and read every RP used oil analysis in the first 40 pages of threads.

The consensus seems to be that it shears down to a 20 weight over 5000 or so miles, but engine wear stays low. This may be where people pick up their .5 HP or 1 MPG gain....essentially it turns into a thinner oil.

Some might argue this is a bad thing, but there were no signs of high wear in these oil analyses either, so the data suggests the RP is maintaining protection, and on paper a thinner oil that can protect against wear just as well is better...

In any event, I'm not worried about it.