Understanding How Odometers Work

Odometers in San Diego, CA

Odometers measure mileage, or distance driven, in cars and other vehicles, and they typically do not account for time a car spends idling or in reverse, neutral, or park. The two main types of odometers are mechanical and electronic. The insurance experts at Tri-Star Insurance San Diego want to help you gain a better understanding of how these two types work.


If your vehicle has a mechanical odometer, you will see 5 to 6 digits in the dash panel that slowly roll over and increase in value as you drive. These individual numbers are connected to small gears that rotate and signify each mile driven. As each number on reaches the value of nine, it turns back over to zero and the number to the left of it rises by a digit. The gears are connected by a band or cable to a special directive gear inside the vehicle’s transmission. Each time the transmission rotates the drive shaft enough times to cover the distance of a mile, the gears turn just enough to move the last odometer digit up by one value.


Electronic odometers are often seen in modern vehicles made after the year 2000, and they work slightly differently than mechanical odometers. Instead of a row of digits connected to small gears, electronic odometers display a numerical mileage value electronically, typically using LED lights. Electronic odometer LED displays are fed information from the car’s onboard computer. The computer receives this information from a magnetic sensor, which constantly measures rotation inside the vehicle’s transmission, and therefore knows how many rotations the driveshafts and the tires are making. Electronic odometers have the added benefit of being more difficult to tamper with, whereas mechanical odometers, especially in vehicles made prior to the 1970s, are quite easily rolled back using reserve spinning of the directive gears.

The more you understand the various parts of your vehicle, the smoother your driving experience can be. If you have other questions about the mechanics of your car, get in touch with American Tri-Star. We are a leading provider of affordable auto, motorbike, and RV insurance in San Diego. Call 619-272-2100 today to speak with one of our knowledgeable representatives and receive a free quote.