STYLETHREAD -- LET'S TALK SHOP!

I've never heard of premium fuel getting better milage - and I've worked in the automotive industry for years. 

I use premium in my car because my engine requires a higher octane level.  I don't see any need to use it unless the manufacturer of your engine recommends it.

ETA:

http://www.cartalk.com/content/features/fueleconomy/

Use the grade of gas you need and nothing higher.

Does your owner's manual say "Premium Unleaded Only"? No? Then don't ever use premium fuel. There. We just saved you 40 cents a gallon... or $8 on a 20-gallon fill up. If your engine is designed to run on regular gas, there's absolutely no benefit to putting in "high test." It pollutes more, it costs more, and doesn't give you any benefit in performance or fuel system cleanliness.

Now, what if your car DOES call for minimum 91 octane? Well, next time you buy a car, dumkoff, check what kind of fuel it requires first. We've always said that once you buy the car, you're stuck. You've got to use 91, because your high compression engine will ping if you don't. But now, most cars have "knock sensors," that retard the timing via the engine management computer (effectively lowering the compression) to protect the engine, in the event that you happen to get some bad gas, or have an emergency and can only get regular grade fuel. So we got to thinking, what would be wrong with using the knock sensor all the time? What if you put regular gas in the car all the time and let the knock sensor do its job and retard the timing? You'd have a little less power, but that extra 8 bucks a fill up might be more important to you than power right now. It would be to us.

It's a controversial theory, we admit it. But that's never bothered us before. And we can't think of any long-term effects of driving with the knock sensor retarding the timing. So our position (for the time being) is... use regular. Who cares? Now, if there are any actual automotive engineers in the audience who have worked on knock sensors, who want to tell us why we have our heads up our keisters, feel free to write to us. And if we're convinced that we're wrong, we'll happily change our recommendation.

-- Edited by detroit at 18:06, 2006-06-15

Nope there is no additional benefit to using premium.  My local news just did a story on it and said there was no additional benefit to it.  My dad says the same thing and he works for XOM.  Also just in case you didn't know.  There is no real difference between filling up with the gas at XOM vs. Circle K (or any cheaper place in your area) per my dad.  The big refineries all produce the gas and then sell it to the smaller guys.  The only difference is the additives that the bigger companies use that don't really add anything to the gas or performance of your car.  Its more of a marketing thing to get into your head to go with the bigger guys.