How many miles can you get out of a 4 or 6 cylinder engine?

Dear Car Talk

Dear Car Talk | Oct 01, 1989

Dear Tom and Ray:

Having amassed over 300,000 miles on my '78 Cutlass with a V8 engine, I'm wondering whether you think today's 4 and 6 cylinder engines could ever boast as much? I've done little other than normal maintenance and frequent oil changes. Most of the miles are highway miles.

TOM: YOU could probably get that kind of mileage out of a 4 or 6 cylinder engine, because you obviously understand the benefits of frequent oil changes, gentle driving, and regular maintenance. Why you'd want to spend 300,000 miles in any car is a question for another day, but let's stick to the mechanical issue for now.

RAY: What makes an engine wear out is how many times it turns. So all things being equal, an 8 cylinder engine should last longer than a 4 because the 8 will turn fewer times to go the same number of miles.

TOM: But all things are not equal. The other thing that effects how quickly an engine wears out is how much "slop" there is between the moving parts. This determines how long it takes the engine to rattle itself into oblivion. Today's engines are built to much stricter tolerances, and have much less "slop" than engines built in 1978. Two other factors favor today's engines. The materials used to make the engines are better, increasing their durability, and the lubricity of motor oil is better today, extending the life of all moving parts.

RAY: It's really a miracle when any engine goes 300,000 miles, so let us offer our congratulations (or condolences, depending on your point of view). We suspect today's smaller engines can do at least as well, but we want you to test our theory. Go out and buy that Yugo you've been dreaming about. Drive it for 300,000 miles, and then write us again and let us know.

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