Dear Tom and Ray:

I recently purchased a used '06 Subaru Outback. It was a rental car that came from the Tahoe, Nev., area. I have noticed water coming out of my tailpipes, and there is a lot of it. At times, it looks like rain. Should I be concerned? I live in Iowa and didn't know if the change in altitude would cause something like this, or if it might be something else. -- Shannon

TOM: Shannon, what the heck are you doing snooping around behind your car? Cut it out!

RAY: Yeah. No good can possibly come from it, Shannon. Especially if the neighbors catch you.

TOM: Actually, the water is nothing to worry about. Water is a natural byproduct of combustion, and seeing it come out of the tailpipe means that the engine is running nice and clean.

RAY: The water might be most noticeable after a series of short trips. Short trips allow water to condense in the cooler exhaust system and accumulate in the muffler.

TOM: On a four-cylinder car, the water will sometimes spray out in spurts that coincide with the firing of the cylinders. I'm assuming that's what you mean when you say it looks like rain. If you're actually seeing a torrential downpour with little bolts of lightning that go from the tailpipe down to the ground, then you may want to get a second opinion.

RAY: But in general, having water come out of the exhaust pipe is perfectly normal. Unlike whatever you're doing snooping around back there.