Regular Unleaded
 

I bought a 2002 C320 2 days ago. I didn't buy from a mercedes dealership but from a carmax which is fine. However, I noticed that sometimes when I am about to stop at a stop light, the car starts to shake (as if it were going to stall out, but doesn't) then it will stop shaking and all is fine. I am definitely taking the car back Monday to have them fix the problem, but I suspect they filled the tank with regular fuel and it had a full tank when I picked it up. It's at about 3/4 of a tank now. Would the fuel cause this? Should I top off with premium? Suggestions?

RE: Regular Unleaded
 

Take it back to them first you paid the premium to buy it at a Carmax so get ur money's worth.

RE: Regular Unleaded
 

Though your car demands Premium gasoline, shaking and trembling at idle speed has nothing to do with octane grade.

There are better suspects...MAF, coil packs, harmonic balancer, etc.

Most likely a sensor issue. A bad sensor so to speak, not bad enough to trigger the CHECK ENGINE light, but just bad enough to keep giving ever-changing values.

RE: Regular Unleaded
 

Some vehicles are prone to water being traped in the fuel injection system. Get a good fuel dryer and add it to your fuel tank to see if that clears it up. Otherwise, you may need your injectors cleaned, professionally.

Hope this helps!

RE: Regular Unleaded
 

For what its worth, I've only used regular unleaded in my 06 C-230 sport since the pulled it out the showroom for me. It runs fine. I have about 3700 miles on it now. I have owned several supercharged trucks and two turbo cars and the only issue with running 87 octane in a forced induction setup is the risk of detonation. For that reason alone I ran 93 octane in those.

RE: Regular Unleaded
 

Thanks for the ideas! I took the car in this morning. Hopefully I will hear something soon.

RE: Regular Unleaded
 

Not too sure why people are so persistant on not using the gas recomended by the Manufacture. There is a reason premium gas is supposed to be used in virtually all Mercedes Benz vehicles that arrive in North America. Though YOU may not notice a difference especially since you claimed to have only used regular since day one, does not mean you can't damage the engine. Is it possible that some of the issues you had with your ML were because of failure to follow the manufatcures reccomendations for vehicle gas and maint.? Perhaps this thread in the Cadillac CTS forum may be of interest to those who don't think there is worth while difference between grades of gasoline (I also own a 05' CTS, so thats why I'm on that forum as well);

http://www.cadillacforums.com/forums...ht=regular+gas

This should sum it up pretty good, we have some very knowledgable people on that forum.

RE: Regular Unleaded
 

All that info is available here. I guess the CTS crowd doesn't know about database searching. They're too busy being "knowledgeable," I suppose.

RE: Regular Unleaded
 

apparently not! otherwise you still wouldn't have foolish people running an insufficient grade of fuel in a premium car :) If you can't afford the premium fuel, then maybe you shouldn't be driving a premium car IMHO

RE: Regular Unleaded
 

The CTS people are apparently not knowledgeable?

You don't know what grade fuel I use in my car, do you? The answer is "no" in case you're wondering.

Don't get an ulcer over what other people run in their car. It's not your call.

Thanks for your humble opinion. Please drive through.