A car engine basically has thousands of mini explosions happening inside of it, is has parts moving very fast and generating tons of heat, and experiences extreme temperature fluctuations on a daily basis. Yet it is the part that usually dies last in a car.
How do they make them last so long and why are we unable to make other parts of the car as long lasting, such as tires and brakes?
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The critical moving parts of the engine are oil lubricated and sealed inside the engine.
The oil provides a protective coating against contact with water and oxygen, and more importantly against metal on metal contact.
The purpose of the oil is to prevent solid surfaces from contacting each other, which would have lots of friction, wear, and heat. Heat would accelerate the wear, and the engine would seize. This happens when an engine isn’t properly lubricated.
Tires and brakes serve a much different purpose.
Tires NEED to be outside the vehicle for reasons I hope are rather obvious. That means no protection from weather, UV, or oxygen. That’s one of the reasons tires are black. Black pigments do a better job of blocking UV radiation from damaging the tire.
If we wanted tires and brakes to last longer, we could devise systems that coat them in oil. I’m hoping it’s also obvious why that might be a bad idea. The purpose of the tires and brakes *require* friction. Friction comes with wear and heat and more wear. There’s no way around it.
We can make harder tires that wear slower, but they wouldn’t grip as well.
In addition to friction and wear being part of the design, there are other design factors such as cost.
Brake rotors are chunks of metal that are going to wear away and undergo intense heat cycles. Under normal use, they’re *going to wear*. They’re in quite literally the worst possible environment – close to the road, getting wet, in contact with road salt, and undergoing intense heat cycles. Given that they’re going to be a wear item anyways, cost is a big factor. Cast iron doesn’t stand up well to corrosion and exposure, but it’s cheap and has all the other good properties.
Another reason engines last long is because oil changes are the one piece of maintenance that every car driver knows about. They’re the most frequent, they’re inexpensive, and even easy enough to do at home. Other service is not only more difficult, but it’s simply not required as frequently. As a result, it’s easier to forget about and be overdue on.
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