We have a Mercedes 320 E ........... is it really important to put the premium fuel in it ?

Try the cheaper gas once when your tank is almost empty. Only put a few gallon in it. If you hear a rattling under the hood when you accelerate slightly going up a hill then you need the better fuel. Otherwise you're just wasting your money. Some people don't believe this but even that rattle (if mild) will not hurt an engine. The sound is pre-detonation (the fuel lighting due to compression not the spark plug ignighting it) It is not any parts in the engine banging together.

The car has a sensor on it that keeps it from knocking so even if you run lower grade gas it wont make noise. However if you want your car to run correct you need to run premium gas. Since its summer time and my guess is your using the a/c its more important.Also since the car is looking at how hot the burn in the cylinder is it will try and add more fuel to increase power to what it thinks is should be this means less miles per gallon.

In cooler times you can use lower octane gas but I would not.

Other than worse mileage and engine knocking, you can (and probably will) destroy your catalytic converter by running a lower octane fuel. I am not certain the cost of this part for your car, but knowing what it costs for Mercedes parts in general, I would (and do) run the premium fuel in my car.

Well, if you want to preserve the life of your engine I would recommend Premium or at least 89. You have an Inline-6 running 220bhp, but with the wear i'd give it 195bhp. I'm not quite sure if your car has knock sensors but assuming it doesn't you're going to have some problems.

If the gauge says; PREMIUM FUEL ONLY, than that's the deal!

A damaged engine is MUCH more expensive than the difference between $2.90 and $3.10 ........

No, however, the engine will last longer. Bear in mind though, that those cars are well built anyway , and should last 10-20 years no problems..

some friends of mine have a '99... their dealer told them to put regular fuel into it and not premium, though it would affect their mileage.

call your dealership, they should know. good luck.

I would fuel the Mercedes with all the sh*t that's coming out of your mouth you Nazi pig....burn in hell Hitler!!!!!

nah