Leaded v. unleaded gasoline...

Dear Car Talk

Dear Car Talk | May 01, 1992

Dear Tom and Ray:

I have a friend in southern California who is the proud owner of a beautiful, low mileage, 1974 Mercedes 450 SEL sedan. This car belonged to her 92 year old mother, who drove it very little before retiring from the driving scene. She tells me that she can no longer get regular leaded gasoline and is forced to use the un-leaded kind. What is this going to do to that great, big V-8 engine?

TOM: It's going to turn it into garbage, Bob. So just leave the keys under the mat, and out of the kindness of my heart, I'll be there first thing in the morning to take this terrible problem off your hands for you.

RAY: Don't listen to him, Bob. It's actually nothing to worry about. One of the reasons they put lead in gasoline was to protect the valve seats, which get pounded by the valves every time they close.

TOM: But the valve seats on a Mercedes are pretty tough. They may wear out someday, but that could be many years from now. And if the seats ever do wear out...you'll just have to have them reupholstered.

RAY: Seriously, Bob, valve seats can be replaced. On an average car, valve seats cost a few hundred bucks.

TOM: So on a Mercedes, it'll probably be about $1,000-- or just slightly more than you pay for an oil and filter change.

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