2001 Mercedes E320 Regular Gas Risk

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MAURO_GARCIA
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I have a 2001 MB 320E with 80,000 miles. I have always used Premium Unleaded gasoline but with the prices being so high now, I am tempted to fill-up with Regular Unleaded. Will this harm my car's engine?
May 17, 2006 at 9:34 AM
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LOSONE
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if your owners manual calls for premium you should use it. You cylinder heads are made of aluminum and unnessary pre-detonation can cause damage. If you go to one grade lower and it "pings" the knock sensor will retard the timing 4 degrees. This may be enough to allow the usage however the loss of power will reduce mileage and it will add up to the same as premium.

Like me with an RV (8mpg) if you own an expensive toy we have to pay the price.

Good luck
May 17, 2006 at 10:42 AM
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Suggested Repair

Use the premium fuel grade specified in the owner's manual. Regular fuel can cause pre-detonation that may damage the aluminum cylinder heads. If a lower grade causes pinging, the knock sensor may retard timing, reducing power and mileage enough to erase any fuel-cost savings.

Conversation Summary

The owner of a 2001 Mercedes E320 with 80,000 miles asks whether regular unleaded can replace the premium fuel previously used. The expert advises following the manual's premium requirement because detonation can damage aluminum cylinder heads. A lower grade may be tolerated if the knock sensor retards timing, but the resulting loss of power and mileage can offset the lower pump price.

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