FUEL: Premium or Reg. 1992 300E 112,000 mi.?

Frank, I hear you.... I use regular in my 300E when prizes are up and I can not notice any difference. Caveat... do not floor the gas pedal to avoid preignition, drive gently .... which I'm sure you do anyway. I do hear that your milage will decrease but I haven't been able to verify although I've tried

cheers, guenter

The cost of the frequent oil changes more than covers the premium fuel's extra cost for those miles. It will be another 15 to 20 years at 7.5K miles/yr before this motor is ready for an overhaul - in about 2023 or so.

Use premium gas if the engine's compression ratio is 10:1 or higher and change the engine oil and filter every 7,500 miles. Regular gas preignites (knocks), especially in hot weather and high loads, so the computer retards the ignition to reduce the combustion temperature and efficiency (mpg) falls.

The greater the demand put on the motor the more it needs premium gas. You might try mid-grade during the winter and switch to premium in the summer.