It has been a few years since I shared the article from Forced Performance on oil choices.We have been recommending Valvoline VR1 since even before that article. With the help of Daniel Satnik we have made some additional discoveries since then.
Even though Valvoline VR1 10W30 and Valvoline 20W50 show the same zinc content, the 20W50 has a stronger film strength that will offer more protection for your turbo. We are now recommending VR1 20W50 for anyone running over 17psi of boost/300whp.
Another thing we run into is: My upgraded turbo died after one week, but my old CT26 was still running fine on the same bad oil for 30 years. I'll admit this one stumped me for a while, but I think I have a handle on it. "Work Hardening" Basically the original turbo bearings were subjected to a fairly casual start of life, running stock boost for tens of thousands of miles. While this was happening the turbo was getting heat cycled over and over and over. This basically heat treated the soft brass bearings into something harder and stronger. New/rebuilt turbos are often subjected to immediate high loads/high boost. We are now suggesting a 500 mile break in at the lowest boost level you can run/10psi. This will give the new bearings some heat cycles and allow them to harden up a little.
Rotella Diesel Oil. I don't use it. I don't have an opinion of it. I don't really understand the appeal except that everyone tells me how cheap it is. I know it's $19/gallon, but six quarts of VR1 20W50 is currently only $33 shipped from Amazon. That's $22/gallon. Surely protecting your engine and turbo is worth the extra $3?
UPDATE: OK, so this opened up a few questions. First, I am personally using the conventional VR1. It's about half the price of the synthetic, and offers excellent protection. The synthetic might last longer between oil changes, but otherwise I don't see a need or value in it. I recommend changing at 2500-3000 mile intervals.
Stock - VR1 10W30 probably more protection than you need, but it's not a condom you aren't missing any sensation.
mild - up to 16.5psi and 299whp - VR1 10W30 has proven fine for these cars
maxing out the stock motor - 300+whp and 17+ psi - This is where I start switching to VR1 20W50
EXCEPTION #1 - ball bearing turbos don't need the thicker 20W50 oil so we actually run them up to about 450whp on VR1 10W30
EXCEPTION #2 - all ATS 2.3 stroker motors are built for 20W50 oil.
EXCEPTION #3 - Altitude. Thinner air requires more turbo rpm. Anyone above 4000ft elevation should be running 20W50. Just be sure to let the engine warm up before aggressive driving.