I think its only the Series III 3.8L's that GM says can use 87. The Chevy's have the Series II motor like the 97-03 GTP's. The 04+ Grand Prix's are the only ones that have the Series III as far as I know. Personally, on ANYTHING with boost (turbo or SC), or high compression, I would use premium all the time.
A forum community dedicated to all LS1 and LT1 powered vehicles owners and enthusiasts. Come join the discussion about performance, specs, builds, conversions, swaps, modifications, troubleshooting, maintenance, and more!