can you use regular unleaded gasoline instead of premium gasoline

I think that you can but you'll probably want to continue using premium. The engine will run better and longer if you use the recommended octane. But yes, you can use regular unleaded.

Your car will run just fine on any good quality Mid-Grade gasoline. Some states have only "up to" 10% Ethanol. To bad you can not find Ethanol free gas in many areas. Your car will love it - but it is usually very overpriced. Even high performance engines such as in the 550's will run fine on good quality Mid-Grade. Try to stick with Tier 1 gs whenever possible.

A HUGE marketing research study, Optimized chemical mechanism for combustion, the MIT researchers deemed AKI — and more specifically, MON — to be an outdated measure of engine performance, originally designed to apply to older, carbureted engines rather than modern, fuel-injected engines. To bring the octane rating system up to date, the team considered doing away with MON, and basing engine performance solely on RON. " Virtually nothing is gained by filling up with a premium or more expensive grade of fuel than the vehicle manufacturer has recommended, the experts say. And many of the same experts explain that drivers may not lose much performance from their cars by using a lower grade of fuel than recommended by the car manufacturer. There is little difference in energy content of regular versus premium gasoline. They both contain about 111,400 British Thermal Units of energy per gallon. The price difference, however, between the fuel grades is anywhere from 20 cents to 40 cents, depending on where you live in the United States. The experts' consensus goes against the long-held belief by thousand of drivers who fill up with premium only, or on every third or fourth trip to the pump. The idea is to fill up with premium every so often to clean out the engines or rev up the performance of older engines. But according to the experts, this practice is like tossing quarters in a wishing well, since most engines are designed to operate on relatively low-octane regular unleaded gasoline."

I agree with Auto_Centric. However, my own personal experience with BMW and MB is that their high performance engines seem to have a noticeable difference on Regular gas. However, Mid-Grade seems to run just fine

I have a 2004 MB and my son accidently put $10 or reg gas. I got upset because now I don't know what's going to happen to the car. I am use to putting premium only. Could anyone tell me what I should do. Should I drive it to waste the ref gas or mix it with premium gas or ???? Thanks

I have a 2004 MB and my son accidently put $10 or reg gas. I got upset because now I don't know what's going to happen to the car. I am use to putting premium only. Could anyone tell me what I should do. Should I drive it to waste the ref gas or mix it with premium gas or ???? Thanks

Just drive your car like you normaly do, my 2006 E320 4matic has never seen 93 octane gas since i owned it, i buy the cheapest gas i can find, an she runs like a champ, engine oil grade is far more important than gas grade.