Already posted this story once before, but I feel the need to post it again since this thread is relevant.

An ex of mine never did car maintenance on his car he owned for 6 years, and the car itself was already over 10 years old. He never even changed the oil once. He didn't drive it very far, just to the university in Tucson and back, so he reasoned he didn't need to bother with the maintenance. Well, I was moving out of the dorms and storing my stuff at a friends place, and he figured he could help. However, he would have to drive on the highway for the first time ever, meaning he would have to exceed 45 mph for quite a long stretch.

10 minutes into his journey (I wasn't with him), he hears a loud bang which, to him, sounded like a gunshot, and suddenly his cab is filled with smoke and there is fire coming from under the hood of his car. He managed to get it to the side of the road and a police officer happened to be behind him and put out the fire with an extinguisher.

Turns out, not taking care of an already old car put a lot of stress on the engine. One of the pistons* actually failed and ended up being thrown straight into the cab of the car through the dashboard.

The lesson he learned from this? Always keep a fire extinguisher in your car. (He still didn't believe in car maintenance, even after this.)

(The real lesson is maintain your damn car!)

*Edit: I've been informed it was probably a rod, not a piston, that got thrown.