What is an Odometer?

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  • Written By: R. Kayne
  • Edited By: O. Wallace
  • Last Modified Date: 18 October 2019
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An odometer tracks the distance traveled by an automobile, truck or other vehicle, and is featured in the dashboard. Motorcycles have one fixed at the base of the handlebars, into a dash, or atop the gas tank. It can be mechanical or digital.

A mechanical odometer basically consists of a series of cogs featuring numbers on each edge. The cogs turns in accord with wheel rotation via the cable and drive mechanism. The mechanical parts are hidden from view by a windowed casing that reveals only a single row of numbers, which displays current mileage. This can be viewed on the speedometer face. Depending on the age of the vehicle, a mechanical odometer might have a maximum count of 99,999 miles, at which point it rolls over to start recounting from 00000 miles.

The modern electronic or digital odometer tracks mileage using a computer chip. The readout is digitally displayed and the mileage is stored in the main engine control module. Manufacturers hoped the electronic version might prevent fraud, but this hasn’t been the case.

Resale value of a vehicle is based in large part on mileage. All else being equal, the fewer miles a vehicle has, the higher the resale value. Odometer fraud, or clocking, involves manually setting the readout back to falsely deflate mileage and inflate the value of the car.


Clocking a mechanical odometer is a fairly easy task. Dishonest private parties and unethical retailers can remove the device, manually turn the cogs to display the desired mileage, then reinstall the device. Innocent buyers can pay hundreds or even thousands of dollars more than a car’s actual worth, often discovering fraud too late.

The automobile industry expected the digital or electronic odometer to significantly reduce fraud. However, tools needed to legally calibrate digital odometers for legitimate purposes are readily available online and off. These tools are known to be used to set back digital devices. Experts claim this is actually easier than turning back a mechanical one.

To protect yourself against odometer fraud, compare the mileage on the vehicle with the title. Each time the vehicle changes hands, the mileage must be listed on the title. If the vehicle is newer, with 20,000 miles or less on the odometer, it should still have the original tires. For older cars with low miles, check wear on the gas, brake and clutch pedals. Ask for maintenance records and/or smog check records and note the mileage.

If considering a car with a mechanical odometer, the numbers should line up evenly. If they are crooked or visibly move when you rap the dash or the face of the readout, experts advise walking away.

Finally, utilize a company like CarFax or AutoCheck to receive a report on the vehicle using the vehicle identification number (VIN). These reports not only verify mileage readings, but will list accidents, flooding, or other reported mishaps that have befallen the vehicle.


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Post 3

Odometers are not the only indication of a car's condition; some people drive a lot but take very good care of their cars otherwise, while other people might constantly do things like stall or rev the engine, forget to change the oil, and otherwise poorly maintain the vehicle, yet drive very little.

Post 2

I remember in the Roald Dahl book Matilda, her father is a car salesman who routinely practices odometer "adjustment" with his cars, to convince people to buy them. While I have never actually heard of this happening in the real world, I'm sure it does, otherwise I don't think that Dahl would have come up with it.

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