also i was told as a rough estimate basically 4 cylinders you use 87, v6 use 89, and v8 use 93 is that true?
Not necesarily. I run my 03 Crown Vic Sport V8 on 87 and it runs just fine w/ no ping. BUT, it is not boosted so if I don't get any spark knock/ping, then 87 is fine. Filling that 20 gallon tank with 93 is not what I'm looking to do if I don't have to

I also run my 00 Grand Prix GT and 95 Bonneville SE on 87 and they seem to do just fine. Haven't lunched a motor yet due to knock. Stop listening to people that may give bad info, read the owners manual for EACH car you own and follow their recommendations for octane levels and you should be fine.