Engine oil Shell or AMSOIL

Whatever full synthetic is on sale, last time it was Rotella T6 15w40, every 5k.

I run t6 15-40 in my 07 lbz with the cat oil filter adapter.

I’ve been using t6 with pretty good lab analysis but I’ve been considering switching over to amsoil.

I run Amsoil 5w40 warmer temps and Ravenol 5w30 colder temps.

Since getting my tune I run Rotella T6 5w-40

Stage 2+ 2016 wrx here, in my experience (with having run both full synthetic amzoil and motul) I can honestly say that while both are rated very good for the FA-20 I would lean toward the motul simply for responsiveness. The car just seems to respond better to that brand, 100% just off personal experience

Walmart. Shell Rotella 5qt for $20. Or Mobil1 for less than $25 if they're out of the Shell and K&N filters always in stock.

You can't go wrong with the Amsoil XL. I run OE 5w30, which offers plenty of protection for a stock engine. Unless your tolerances and clearances have changed, there is no reason you need 5w40. Modern synthetics, especially ones designed for the extra heat of a turbo, are outstanding oils.

Anything is better than nothing. I've tried most big oil brands but overall I like the Shell Rotella stuff most.

I use the T6 as well and like it a lot. Other people in this forum have recommended in the past as it’s additives are supposed to be good the 4.0’s. Always worked well for me, it’s reputable, not the most expensive and if the additives do actually help, thats only ever a good thing.