Dear Tom and Ray:

My neighbor warms up his diesel F250 pickup truck every morning for 20 minutes. He says he is "protecting" his investment, as he just got a new $5,000 engine. I say he is killing his neighbors. I can't find anything on the Net about warming up a diesel engine in San Francisco. I've only seen suggestions that you warm up a car in really cold climates. What's up with this? -- Sue

TOM: Has he made an offer on your house yet? I think he's trying to smoke you out, Sue.

RAY: There's absolutely no good mechanical reason for him to warm up his truck like that. It shouldn't need to be warmed up at all in that climate. Ever. It's certainly not doing the engine any good.

TOM: All he's doing is wasting fuel and getting himself uninvited to the hot-tub party you're having Saturday night with 24 of your sorority sisters. Mention that the next time you see him, and see if the light goes on.