What type of gas do you run in your 08 malibu? Reg, Med, or Prem? Is there any benefit to running Prem in a 4 cylinder? Any extra HP, gas mileage?

The manual calls for regular and that's what I use. The only stipulation is I always use a Top-Tier gas (http://www.toptiergas.com). In my area that would be Texaco/Chevron or Shell for their extra detergent additives.

I'm surprised Exxon/Mobil and BP are not listed among the 'Top Tier' companies.

As Pizza Man said, regular unleaded is what the manual calls for and that's what I'm using.

Maybe a bigger concern now is brands that use 100% gasoline or 90% gas/10% ethanol (E10). Around here (Allentown, PA), stations such as Sheetz, Wawa, Hess, and Sunoco have signs on their pumps saying the fuel may contain up to 10% ethanol, while Exxon and Shell don't have those signs, yet. So far I've stuck with the stations that aren't using ethanol, as the price is practically is same. Maybe down the road I'll start using E10 fuel.

I tried using Mid grade and Super. I got better engine response and smoother acceleration....but my MPG's actually went lower. So, I'll probably just fill up on mid-grade when I take long car trips.

I only fill up with BP gas, and I use regular on my LTZ.

You know people think Mid and Super grade are better then Regular and sometimes that is the case but the higher grades of gas have more detregents in them, so if you run them in the car all the time its not good for the engine. Its just like fuel treatments you only put them in every certain amount of miles becuase if you put them in all the time it can eat away at the engine's components.Thats why Chevy is recommending running Regular in the Malibu.

Question: Are the 08's FLEX FUEL also or is that something that has to be specified?

Just avoid ethynol all together. Even though you save a few pennies at the pump the mid grade (regular unleaded) will give you much better fuel mileage, thus saving you money. Most manufacturers would tell you the same thing as ethynol chemical properties are not as stable as regular unleaded i.e. air in the fuel, expansion/contraction of the fuel, capabilities of creating moisture in the tank in cold weather, starting issues, clogging injectors and burning the fuel hotter than what the engine was designed to do. High octain premium is not practical as it has no effect on mileage in these cars and costs more.

I can't seem to understand the concept of Ethanol....I mean, it greatly reduces your fuel economy, doesn't cost that much less, and takes away from the corn supply. So, now things that use corn (food and otherwise) is going to cost more....Even if I had a Flex-Fuel vehicle, I wouldn't put in the Ethanol because I would have to visit the pump more often!

Question: Are the 08's FLEX FUEL also or is that something that has to be specified?

No, the Malibus are not FlexFuel (E85) capable. I believe all GM vehicles that are FlexFuel capable will have a small badge on the rear (see Impala or Tahoe). Supposedly, all cars are E10 (10% ethanol) capable.

Ok gotcha...I've seen the logos on them but I wasn't sure if all GM lineup would be flex from that point on.

From what I read, pure Ethenol isn't that great anyways. According to the article it burns away quicker causing you to fill up more frequently.