Car Talk: Can working on a car increase the odometer?


CAR TALK

By Ray Magliozzi - Car Talk



Dear Car Talk:

Will a car’s odometer increase when being driven stationary on a mechanic’s lift in a garage? — John

Let me guess, John. You took your car into a shop and it came back with 75 extra miles on the odometer.

You went to the mechanic and said, “Hey, what’s this?” And he said: “Oh, gee, my assistant, Walter, had it on the lift, listening for a noise, and then the burrito truck showed up. So he went for a burrito, then he got into an argument about carnitas versus tofu. Then, after the burrito, he spent 45 minutes in the bathroom, so an hour later he came back and there were 75 miles on the odometer.”

And your mechanic emphasized that the miles were definitely not put on by his nephew, Horace, who definitely did not drive it to an out-of-state party at Phi Kappa Barfa last night.

Well, the answer to your question is yes, the speedometer and odometer will move if a car is driven on a lift.

When the car is in Drive, the wheels are turning. And when the wheels are turning, the vehicle speed sensor is picking up a signal, and that’s what moves the speedometer and odometer.

And there are often good reasons for running the car in Drive up on the lift. If there’s a noise or vibration that only occurs when you’re driving the car, that can be the best way to figure out where it’s coming from. On the other hand, that kind of diagnostic work should rarely add more than a handful of miles to your odometer.

Think about it. If you put the car on the lift, and put it in Drive, the engine is running at idle speed. The wheels are turning lazily, at the equivalent of maybe 10 mph. At 10 mph, if you run it for six minutes, that’s a mile. More often, we’ll be trying to find a drivetrain noise that only occurs at a certain speed.

Let’s say we heard the noise at 60 mph during our road test. Then we’ll put a guy in the car while it’s up on the lift and tell him to bring it up to 60 mph while another guy is listening underneath. But even that process only takes a minute or two. And even at 60 mph, that’s two miles on the odometer.

So — including the mechanic’s test drive — if you’ve got more than 10 extra miles on the odometer after a trip to the shop, your mechanic owes you an explanation. There may be a legitimate one. It may have required several long test drives to get the problem to occur. But if you see a bunch of empty red Solo beer cups in the back, be skeptical, John.

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CAR TALK

By Ray Magliozzi

Car Talk

Got a question about cars? Write to Car Talk write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

Got a question about cars? Write to Car Talk write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

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