My 1994 C180 Euro seems to be running better on regular than premium. Why I don't know. Besides saving on about A$0.05 to A$0.10 per litre, it makes the motor smoother with less vibrations when on "D" at idle especially at traffic lights. Less vibrations when I change to "N", but this is not necessary at traffic lights. Is it ok to run on regular or can I do full premium, then full regular and so on or just fill half of each every time??? Will this damage my motor which is only a 4 cyl, twin cam , 16 valve, fuel inj 1800cc motor? The car is only 1350kg kerb weight, but feels and looks like its 2000kg. The tyres are 195s on 15inch Benz steel rims. Your expert advice will be appreciated.

Mercedes Benz new what they were doing when they put Premium fuel only on the level indicator. I wouldn't risk it, if its not running well with premium there is a problem. Good luck

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Brandon



2008 S550
1957 Dodge D100
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2001 Suburban
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The owners manual has the answer. Use at least whatever octane rating is in this manual.

hocky1,

When you refer to regular and premium, what exact octane levels are you referring to? As mentioned already, just check the manual and use whatever minimum octane it says your car requires...I have never heard of a car running better on an octane that is LOWER than the recommended octane...unless your knock sensors have retarded something in your engine to compensate for the lower octane, and thereby making whatever that caused the roughless in your engine with the recommend octane less apparent...however, I doubt this is likely...with my '95 E420, the manual recommends 91 octane or above...as you know, oil prices skyrocketed a little while ago, and I switched from 94 octane to 92, and felt the car accelerated/idled very rough...when I came back up to 94 octane, the car felt fine again...but many argue that higher octane than what the manual recommends is useless...oh well...who really knows...

Regarding your car feeling heavy, you could upgrade your shocks, springs, and move to a more aggressive tire/wheel package to bring up the handling...

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1995 black pearl/black Mercedes-Benz E420 :

92 or better. Most all the gas MB engines, at least the US models, have at least 10:1 compression ratio.

Good luck,