Friend your dead ass wrong. I could use Pennzoil 5-30 Dino oil if that is within the viscosity parameters my owners manual calls for and not void or have any warranty issues. The oil cap is the marketing agreement. Any oil that has the API rating and the visocisity parameters as called for in the owners manual is all you need to stay within the warranty requirements.
Mobil1 is OK oil. Nothing to right home about. TBN's are so so. Shears down is no secret. Overpriced for what it is. VOA's/UOA's reflect middle of the road results. Castrol GTX dino with 5K OCI's are even better. RedLine/Royal Purple results are better in the synthetic world. But to say Mobil1 or you void your warranty or have any warranty issues is ridiculous.
Fairly simple question of Royal Purple vs. Mobil1.
Lets look at the VOA's of the two in the 5-30 viscosity arena.
Let's look at the friction and suspension (detergent) specific characteristics/make up.
Royal Purple Racing 21 ( 5-30)
Moly-130
Calcium-2944
Phosphorus-1130
Zinc-1981
cSt @ 100c-11.2
Mobil1 5-30 ( New EP)
Moly-79
Calcium-2936
Phosphorus-955
Zinc-1070
cSt @ 100c-10.6
Basically the same price but look at the delta between the two!
Now lets look at say RedLine 5-30.
Moly-679
Calcium-2917
Phosphorus-1419
Zinc-1421
cSt @ 100c-10.8
So as you can see from these VOA’s done by Blackstone, Mobil 1 is the weakest of the three. Does that make Mobil1 bad? Nope. But there are better in that price range for sure.
Use any of these oils while under warranty with no issue whatsoever.
For your viewing pleasure from GM.
http://www.gmgoodwrench.com/_res/pdf/SimpMaintConsumerQA.pdf
On a side note: I see you and I are about the same age

Old fella's

I also have been drag racing and building street beast since the early 70's myself. Cool:cheers
My poor old 04 Goat.........