Cats love a nice warm engine block. Especially in the winter, when it's really cold, and the farm cats have nowhere to go. After all, nobody will let them in the house, the barn hasn't got any more hay in it because the farmer keeps feeding it the horses. The milk the farmers wife put out for the poor farm cats is frozen solid, and the field mice are all deep in their burrows.
So what's a cat to do? Hey, farmer man just got back from checking the cows and chopping the ice off of the water troughs, and has gone inside for lunch. The engine in the truck is nice and warm, so cats tend to climb up inside and snuggle up to the nice warm cast steel, so as to thaw their frozen paws. Little do they know that the farmers wife is going into town to get the mail right after lunch, so when the engine starts up, sometimes the poor unfortunate at the front of the engine uses up the rest of his nine lives. Some cats are luckier, and escape with only a broken tail, others go to town and back. Sometimes the ones that go to town hop out when the truck stops, and either stays in town for the rest of their lives, or slowly makes his or her way home cross country. This has happened. At least, my Dad's old blueheeler (a dog) did it, and I bet a sufficently motivated cat could too.
We once had a cat break it's tail in the fan of an engine. The end of the tail wasn't severed, it hung on for quite some time. Now, this was a cat that my sister had adopted, and it had graduated from farm cat to house cat. It was named Taffy, because it left paw prints in a batch of taffy that I had left on the counter back in my candy making days (late elementery school). So anyway, this cat slept in my sisters bed. One night, the end of the tail, about three inches of it came off. In my sisters bed. She flipped. I was amused, the fact that she was freaking out was even more amusing. Her mean brother (me), thought the end of the tail would have made a great key chain. Sort of like a rabbit's foot, but not. I called the cat Stubby after that.