Oil in an air filter? That's your cue to get a new car.
I have a 1982 Honda Civic. Why does my air filter have oil in it?
RAY: Have you seen those new toothbrushes that tell you when it's time to buy a new one? There's a blue line on the bristles, and when the line disappears, you're supposed to throw that toothbrush away.
TOM: Well, oil in the air filter is the automotive equivalent of the blue line on the toothbrush. This is your signal to go out and buy a new car.
RAY: Right. You have what we call "excessive blow by." That means your engine is old and worn out, and is burning so much oil that the crankcase ventilation system can't handle all of it. So some of it is ending up in the air filter.
TOM: You can check the crankcase ventilation system to make sure it's working properly, but I'll bet it is. The problem is that you've a zillion miles on an engine that's only a little bit bigger than the one in my lawnmower. And it's had it.
RAY: If you're really in love with this car, and it's in good shape otherwise (be honest, James), you can rebuild the engine and drive it until the body falls apart. But if you've been waiting for a signal from the heavens that calls out to you, saying "Dump it, James...Dump it," this is as close as you're going to get.