Didn't read this entire thread, I just read OP's post...FYI.

If you're just normal driving and driving spiritedly I don't think it matters what brand you use, I personally use Castrol because it's cheaper and it works like the higher end oils for what I do.

I've ran Mobil1, AMSoil, Royal Purple, eventually I finally figured out that those damn oils are EXPENSIVE! Especially since we use almost 6 quarts!

I switched to Castrol oil (Edge EP or Edge) and from my experience.....the car drove the same. I daily drive and drive spiritedly, drives the same and great.

I also only ran 0W-20 when I was NA, I switched to 5W-30 because I read around a while back and it was recommended to do 5W-30, overall car still drives great as usual!

I'm sure if you're tracking hard you're going to wanna use the more higher end oils like AMSoil or Motul but if you're just DDing and spiritedly driving I honestly believe you're just spending more money for no reason.

To add to this post, I just called P&L up in Chicago and EVEN WITH WINTERS they said 5w 30 was fine but even recommend higher grade, FI. They even recommended up to 40... Kinda of gauged my eyes there

This is somewhat out of left field...

When I used to own WRXs (2.0L '04 & 2.5L '07) if I ran 5w30 mobile1 full syn. both cars would burn oil half a quart to a tank of gas. I switched to German Castrol 0w40 full syn. On GC neither car burned oil. I did 3k mi. oil changes. Owned both cars to close to 100k miles. Both cars were tuned. the 04 had a upgraded turbo with all accompanying parts ("stage"3). German Castrol oil never missed a beat. Castrol switched to Belgium country of origin for 0w40 a few years ago. Guess what I run in my BRZ.... Soon to be FI. Just waiting for the slow boat from Aus/Thailand to deliver the my parts.

Buy an oil pressure gauge and then you won't be guessing. Use the thinnest oil that gives you satisfactory oil pressure for the driving conditions you subject the car to.
I've moved to a 0w-40 when I'm tracking and a 0w-30 if I'm not planning any track days soon but I'd happily run either - just keep an eye on the pressures and temps.

I definitely do need an oil pressure gauge.. What are normal oil pressure numbers for a turbo'd 86?

fwiw, I also run 0w-40 castrol edge synthetic for those special additives during my track events. I was supercharged at that point. I've now switched to turbo and don't plan on changing oil specs.

10psi per 1000rpm is the rule of thumb for most engines. It is actually hard.to achieve on this engine at high oil temps. An engine oil cooler is essential I reckon.