Why is having lots of miles on a car bad, and what is the point of miles?
In: Engineering
As an engine runs, it slowly deteriorates. Mileage tells you roughly how much wear and tear an engine has been through, and therefore roughly how much life is left in the vehicle.
Average use is considered about 12,000 miles a year. So if you buy a car that’s 3 years old that has 36,000 miles on it, you know it’s been driven fairly normally. If you look at a 3 year old car with 72,000 miles on it, you can tell it’s been driven twice as much as average, so technically the engine is 6 “average” years old.
Everything wears out with enough use. The number of miles a car has been driven is one measure of how much it’s been used. The age of the car, the way it was driven, and the type of maintenance it had also contribute to it’s condition but are harder to accurately track. Things like tires and brakes we expect to wear out and need replacing but all the important parts of the engine and transmission are inside, where you can’t see them. Even with good maintenance and careful driving, you can expect to have more problems with a car that has been driven 150,000 miles compared to one that has only been driven 70,000 miles.
A mile is a measure of distance. It’s 5280 feet, or ~1609 meters. Cars keep track of how many miles they have traveled using an odometer. More miles on the odometer means the car has traveled more distance, and therefore put more wear on the engine.
If you had the choice between buying two cars that were completely identical except one has 12,000 miles and the other has 80,000 miles, you would want the 12,000 mile car because its engine is less worn out than the 80,000 mile one.
Miles are a good (albeit imperfect) measure of how much wear-and-tear has been put on a vehicle. If it’s got zero miles, that means it’s brand new, right off the lot, no wear and tear at all. And more miles means more wear-and-tear, more likely that something big and expensive will break and need to be repaired. You understand how wear-and-tear works. If you’ve worn the same shirt for years, it’s gonna get stretched, the colors will fade, maybe there’ll be stains, maybe there’ll be some rips and holes, or frayed seams. It’s not worth as much anymore as if it were brand new. If you bought it for $30, there’s no way anyone would buy it from you for $30 now (unless it’s “vintage” but that’s another question).
If you’re trying to sell a used car, the more miles it has on it, the less its worth, because it means it’s taken a lot of wear-and-tear, and the new owner is likely to have to spend more money to keep it running.
The reason cars have odometers is to keep everyone honest. If you’re trying to sell a used car, of course you’d have an interest to say “ah, it’s barely been driven, it’s basically good as new, I deserve almost full price for it.” And the prospective buyer, what’s he supposed to think? How could he know if you’re telling the truth or full of shit? It’s hard to tell how good of a condition a car is in just by looking at it. Even if he were to take it to a mechanic and an appraiser (which would cost $$$), they still might not find everything wrong with it. And most people buying/selling used cars don’t put in this much effort, they want to do the deal simply without having to involve a bunch of extra people to help negotiate a fair deal. But since every car has an odometer that tells you right there how many miles it has, it gives you some information about how much the car is truly worth, you don’t have to just take the seller’s word for it.
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