Will driving a new car fast at the get-go get you better mileage later on?

Dear Car Talk

Dear Car Talk | Sep 01, 1989

Dear Tom and Ray:

Is it true that driving a new car fast from the very beginning, instead of slowly as the book tells you to, will "set" the engine in some way so that it gets better mileage later on? A Toyota mechanic told me that.

TOM: I think this guy's trying to "set" it so that he'll have plenty of business later on. Break-in periods are necessary for most cars. During break-in, when you are instructed to drive at moderate and varied speeds, the piston rings get a chance to "seat"--that is to conform to the exact shape of the cylinder. If they don't seat correctly, the cylinder wall can get scratched and scored, and the engine will burn oil. More importantly, if spaces develop between the pistons and cylinder walls, compression will be poor and power will be diminished.

RAY: Cars used to have an elaborate break-in periods. You had to use special oil, you had park the car facing east in the morning. Now the break-in period is inversely proportional to the quality of workmanship. The average car needs to be driven gently for the first thousand miles or so. A car like a BMW 535i, with its superior workmanship, requires no break in period--the book just cautions you to keep it under150 MPH for a few weeks. On the other end of the scale, my brother is still trying to break-in his four year old Yugo.

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