No less then 91.

 

First of all, I was responding to the tard who said that 87 octane would hurt your motor. These cars are made and required to be able to be compatible with regular unleaded gas and thats all there is to it. Now the computer does pull timing for the lower octane, but it will not pull three tenths off your time.
I have seen my uncle's stock internal (bolt on intake and exhaust) ls1 vette dyno numerous times with 93, and 87 octane. There was virtually no difference on the graph! (less than 3hp) I have also driven my stock 99 ss at the track with 92 and 87 on comparible days and my best times were nearly identical. 13.70 and 13.73.

 

I've been at the track with a friend of mine who still had 87 octane in the tank of his TA as that is what he ran in it during the work week. Once he realized that he had forgotten to get premium, he left the track and filled up with 93. When he came back his times dropped by 3 tenths and he picked up 3mph, and the temps even got hotter out too. His TA was a 2.73 geared automatic and it ran consistent times, so it wasn't as if he drove it better or anything like that.

 

Just like most of you I only use 93 octane in the LS1 just as the manual instructs (never seen 90 or 91 octane around here). I love the car too much to use anything less.

 

All we have around here is shitty 91 :'(

 

I use 87, i havent noticed much difference in anything. Car runs great, and accelerates great. Thinking i should try the 91 but in my mind, Gas is Gas - It detonates and propels a car end of story.

 

93 octane and that only