Which fuel grade is best for 2006 Malibu?

Manual says 87 octane or higher. I have read that if engines with compression ratios of 9.3 : 1 or less will safely operate with unleaded 87 octane fuel. Engines with higher compression ratios usually require higher octane fuels. As www.msn.com data, the 2004-2006 Malibu LT 3.5L V6 compression ratios is 9.8:1. Do we need to use 89 octane or even 93 octane?

In my 04 Malibu 3.5 I have always used 87 octane, no problems yet, 30K. My owners manual states 87 Octane.

Your engine has aluminum heads, which dissipate and distribute heat more evenly than cast iron heads, thus reducing the chance of pre-detonation, so you're fine running 87 octane.

Your engine has aluminum heads, which dissipate and distribute heat more evenly than cast iron heads, thus reducing the chance of pre-detonation, so you're fine running 87 octane.

But I'm looking for lowest build up( carbon deposit) and best mileage.

But I'm looking for lowest build up( carbon deposit) and best mileage.

87 fits the bill, octane enhancers adds deposits. Higher octane has less heat energy.
If a higher octane will give you a good feeling go for it.

Because I disagree with the "higher octane has less heat energy" statement (at least not enough of a difference to NOT call it negligible,) I did a search. I found a really good article here:

http://www.bajajusa.com/High%20Octane.htm

There is some good insight on octane, what it does, and how it works, in layman's terms.

A little side note: I've never run anything besides 87 octane in my car (96 monte 3.1L) and when I replaced the head gaskets last winter after 120K miles, there was essentially nothing built up on the pistons or valves upon teardown, although I've been extremely careful not to go over 3000 between oil changes, and always been on schedule with all other maintenance.

Thank you all. Great information.

Octane rating means only one thing. A fuel's resistance to detonation/knock. It has absolutely nothing to do with a fuel's heat or energy output. Running a higher octane # than your engine needs does nothing but waste money.

Joel