I have a 2006 chevy monte carlo ss. And i am currently using 87 octane. Would car run better with a higher octane? What does chevy suggest for that car?

 

Yes, chevy recommends premium for the LS4.

It has a high and low octane timing table built in, and will switch between the two depending on knock. But you are leaving a lot of power on the table by using regular fuel.

 

Agreed, premium is reccomended.

Will it feel like it 'runs better' to you depends on ambient conditions, how knock prone your engine is, and how often you put it in high load situations. Could range from no noticeable difference to slightly noticeable.

I tried 87 in my GXP a couple times and did get some knock; worse in the summer heat. When the engine senses knock, it pulls timing which lowers power. After playing around with testing, I just ran it on 91 the rest of its life. I figured if I wanted to save money on gas and didn't really care if the engine made all of the power it was rated for, I should've just bought a base model.