I can say that using premium when the engine is tuned for regular won't cause stalling. There are plenty of fools out there who waste their money putting premium gas in their tanks when they only need regular. Their imagination tells them that their cars have more power and go faster with premium and will argue such until they drop, but they never complain about stalling. You have problems when you use regular when you need premium, not when you use premium when all you need is regular. In fact, it's normal practice for gas stations to put premium grade gas in their regular and mid-grade pumps when regular isn't available. Happens all the time.

I've had two different dealerships reload the factory programming on two different cars I've owned after I insisted they do it. They weren't MBs, but that shouldn't make a difference. They should do what sleepwalker is saying and check the engine control programming without your asking for it. They know the "kompressed" engines should run on premium and they shouldn't tell you to run on regular or mid-grade.

 

... and, Europe (and I guess Asia) uses a different formula for measuring the octane rating of gasoline. Comparing USA and European octane ratings is not an apple-to-apple comparison. I think mioCLK has the particulars, if you want them.

Sonoco stations at sea level on the east coast sell 94 octane at their pumps. You can get higher octane from them and other sellers, but not at the normal pumps. It's only worth it if you race, though,... and need it.

 

Actually mine is not a really stall like dxm8693's. It just shakes and does a little vibration sound when I take my foot off from the pedal and it comes to the lower rpms in the mornings. If the rpm is higher than 1000, it is just fine.

 

sounds like it's just a dirty throttle valve or idle speed air valve.

try cleaning them and you will find the problem gone.

 

You need to get it scanned. The kind of adjustments you need can't be done with a screwdriver anymore.

How many miles have you put on at 5 miles per trip?

 

I am at 1000 miles now

 

I just spoke with MB technical rep. from 1800FORMERCEDES who said it was perfectly ok to use 89 octane fuel in this car...furthermore, he went on saying that there is a minimal difference between 89 and 91 octane fuel and it is in detergents only (91 octanes has more detergents which are suppose to keep your fuel injectors clean and minimize carbon deposit)...also, according to him, there is no difference in vehicle performance...I tend to disagree with him because if octanes are measure of resistance to knock, and this turbo charged engine has a higher compression ratio then the lower octane fuel should ignite before it's suppose to...then again, that's the theory...the dealership has said that fuel additives change from winter to summer here in Texas and that the only time they have seen this problem is in summer time (even in S class)...what can I say? They made the car so they must know what they are talking about...I switched to 89 octanes and the problem went away...I'm just surprised that MB would make an engine this sensitive to fuel...I used to drive a GMC truck and you could put clam chowder in it (with a drop of gasoline ) and it will still run with no problems...

 

It's really hard on an engine to drive it that way. A lot of bad stuff will build up over time in the oil and cause problems. You can probably avoid a lot of them if you burn off contaminants once a week by going for a good 20 mile or so highway ride that allows the engine to run for awhile at operating temperature.

Also, get the oil changed more often than recommended. How often? Depends. I'd go with every 2,000 miles or so. Or, use the severe duty maintenance schedule if there's one in your owner's manual. If you want a solid number, you can buy an oil test kit at an auto parts store for about $15/$20. You ship off a sample of your oil for analysis. The results will tell you if you're changing it often enough by identifying contaminants.

What you should really do is get a cheap beater car for going to work.

 

Thanks for your advice. Do you think that this stalling problem might be related to this issue of driving 5 miles each way everyday ?

 

It's doubtful after just 1,000 miles.