i have a non turbo 87 s4 5spd gxl, and its hard to tell if 93 or 87 gas makes a difference. it has header, high flow cat, cat back, intake, coilovers, aluminum drive shaft and some other goodies.
lmk what you guys think.

 

owners manual recommends 87 octane for non turbo.

 

No mods, basically just run 87.

With heavy porting and well tuned intake/exhaust then you can see benefits from running 93 octane or even race fuel. With stock ports, though, you're not really going to be getting enough air into the chamber for compression issues to arise.

 

87 should be totally fine. i caught my 87 GXL ping once, on 87, but it was on a REALLY cold day, and the engine was warm enough to be in closed loop, but cold enough that it wasn't heat soaked yet. if it did knock it would be in the 1500-3500rpm range

 

Just 87 unless you have mods with stock its not going to be worth it

 

I was wondering the same. I was told to run 93 but didnt think i need to