Thanks for the tips! Oil looks pretty clean on the dipstick at least.5w30 is what i run. its a sbc. it will be fine with whatever ha. if you are track driving, different story! and if u are cold starting in -30c, different story!
I track my Z as many times as i can in the summer, and before that was an 86 4+3, i run 15w40 at the track, and only synthetic, due to its resistance to heat breakdown exceeding 300f.
for street driving, long as its clean, really doesnt matter, in my opinion, based on my experience.
On that 86 high miler i had, it wasn’t maintained very good. Lots of hard crusty sludge. Id read a thread on cf about just running the cheapest oil u could find through it because you were only going to let it stay in the engine for a couple heat cycles and then drop change it. This technique worked quite well on that car. when i removed vc’s again a few months later (about three oil changes) it was substantially “cleaned up”. once that was done i then began to run synthetic 10w40 for the track and always had that in there until i sold it.
my high miler had extremely smelly oil! if you dont have nasty oil, you can pretty mich disregard the part about doing a few cleaning sacrificial oil changes
I was leaning towards running Castrol GTX or Castrol GTX High Mileage, 5W30.