Fact or fiction: breaking a new engine at slow speeds will lead to long-term sluggish performance.

Dear Car Talk

Dear Car Talk | Nov 01, 2001

Dear Tom and Ray:

My dear, departed daddy told me that if you broke in a new car engine at slow speeds, it would always be slow and sluggish. Is this true? What's the real skinny? Is there a preferred break-in protocol? -- Susan

TOM: Great question, Susan. But since we never speak ill of the departed, we can't answer it.

RAY: Actually, I'm sure your daddy was right about many OTHER things and was a superior human being in all other regards.

TOM: But his story about break-in is an old myth, Susan. And we don't know how it got started. Probably by some teen-age boy who got caught racing his dad's new car.

RAY: It assumes that the car somehow "learns" to go slow when it's young, and then it never knows how to go at normal speeds later on. Kind of like my brother at work.

TOM: But it's just not true. There IS a legitimate protocol for breaking in a new vehicle. It varies slightly from car to car, but the main purpose is to allow the piston rings to "seat," or conform to the exact shape of the cylinder walls so that they make a tight seal. And most experts agree that the best way to do this is to keep the engine rpm below 3,000 and to vary the engine speed (i.e., don't drive at one constant speed for a long time).

RAY: And the break-in period generally lasts anywhere from 500 to 1,000 miles. Or until your check clears at the dealership, whichever comes first.

TOM: If the piston rings don't seat correctly, your car might burn oil later on. And nobody wants that.

RAY: So the speed at which you break the car in might have an effect on how much oil it burns. But it has absolutely no effect on how fast or slow the car goes.

TOM: Last time we checked, that was mostly affected by the position of your foot on the gas pedal.

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