Ideally analyze the oil first then find the sweet spot for lubricant choices. Every engine is like a fingerprint and using a hand in glove approach can save the engine, get better combustion efficiency, better MPG, and drive smoother. I worked for 45 years as a lubricant and fuels analyst/tribologist. Since I retired I partnered with a friend who is also a disabled military vet like me to market what I used to offer. ISO CERTIFIED OIL ANALYSIS from Nick Mikitka here: Note he is an Amsoil dealer but offers this service exclusively since I retired. He will not steer you to Amsoil or any brand but allow you to decide based on data. He's like me, use what works for the best value and price.
Independent AMSOIL Dealer
Synthetic Advantage LLC
I'm running Havoline Pro-Rs Bio Synthetic 5w30 in the 24,000 miles on my L3B 2.7 Turbo Custom since I saw oil consumption using Amsoil Signature Series 5w30. I suspect the oil control rings got just enough ash deposits that they allowed about a qt in 6000-7000 miles. The Havoline has about 30% estolides biosyn base oil that cleans well. So far at 3200 miles its not using a drop. I drive like a grandpa but I live at 9000' msl in Colorado and I am in 4WD alot because we live on trails up here with snow, mud, ice a 9 mo a year reality.
For you owners that refuse to sample run a DEXOS1 GEN 3 product. The havoline I mention above is a GEN 2 but it did not submit for a GEN license but would pass based on what I am seeing in testing and oil consumption slowing/stopping so far.
I owned my own company and was trained in USN, USA, and Cummins so I have been living better living through chemistry a long time.
More important than engine oil is fuel. More ethanol the better. E15 here is only 86 octane but I run that constantly in the L3B with a tailpipe that's all water no carbon soot from the DI engine.
The Amsoil OE is a Dexos Gen 3 compatible formula and eventually I might go back to that.
Mobil Full Synthetic ( NOT Mobil1) GEN 3 is a sleeper formulation at a good price. Mobil 1 and Royal Purple are good formulations.
Any Dexos1 GEN 3 will have more real synthetic and lower sulfated ash content so you don't make deposits in any of our engines. Note NOTHING will stop defective valve train components in the 6.2 or 5.3 so all you'll do is delay the inevitable with the engine oil being better, fuel dilution of our engine s is a real thing and interrupts the oil ability to protect the crappy V8 valve-train alloys for many of the Trail Boss and other GM trucks. In the V8's the Amsoil Signature Series does help the valvetrain issues but generally won't stop it if you get defective alloys.