Dear Tom and Ray:

I discovered your column recently, and have been reading it ever since. There is something I have always wondered: How does the oil circulate in a car?
Kara

TOM: Good question, Kara. It's a lot like the way blood circulates through the body. But in the engine, the "heart" is the oil pump.

RAY: Obviously, when you dump the oil into the engine, it goes to the bottom--to the oil pan--and it sits there.

TOM: Then, as soon as you set the engine in motion by turning the key to the "start" position, the oil pump starts pumping--that is, it sucks oil in at one end, and pushes it out the other end. It sucks the oil out of the oil pan, and then pumps it and sprays it to various parts of the engine.

RAY: The idea is to constantly lubricate every part of the engine where there's a potential for metal to touch metal. What the oil does is form a protective film between the metal parts (between the crankshaft and the crankshaft bearings, between the piston rings and cylinder walls etc.) and keeps these parts from actually touching and destroying one another.

TOM: And there are passageways, just like the arteries in your body, that carry oil to all these places. They're called "oil galleys." For example, the oil that has to get to the crankshaft bearings actually passes right through the center of the crankshaft.

RAY: On its way to all these places, the oil also goes through the "oil filter," which catches any contaminants, pieces of metal, or stray farm animals that have somehow found their way into the crank case.

TOM: Then the oil flows back down to the pan, where the oil pump sucks it up again and the whole process starts over.

RAY: My brother's 1963 Dodge Dart has one additional step. On his car, as the oil drains back down to the oil pan, it leaks out about 40 different holes.

TOM: Hey, it's going back into the ground. I'm recycling it! 1912