Q: My local dealer has changed the oil on my ’99 Neon since we bought the vehicle new from them. Oil started leaking from the drain plug the last time the oil was changed. They told me that aluminum oil pans wear out from multiple oil changes and that it would cost $475 to install a new pan. Is this right? I figure they’re the ones who’ve been pulling the plug in and out, and they’re the ones responsible for it.

A: Heck, I’ve worn out the threads on a steel oil pan! Depending on how many times the oil has been changed — let’s see, maybe three times a year for 10 years — it’s no surprise that the threads in the oil pan are worn to the point of dripping oil. I’d be more concerned with the drain plug loosening and falling out.

Unless there’s evidence of overtightening, my opinion is that this is your responsibility, not theirs. But before I replaced the oil pan — $232 for the pan and 1½ hours of labor to install it, according to my Alldata database — I’d check with an auto-parts store to see if there’s a longer or oversized drain plug that would fit. There are also rubber replacement oil pan drain plugs to address this situation, but I’m not entirely comfortable with those.

A quick look online pulled up an aftermarket replacement oil pan for less than $100.

Q: I have an ’02 Cadillac SLS with 175,000 miles on it. A month ago, it would not idle after a cold start. The map sensor was replaced, the throttle body and mass air flow sensor were cleaned and a fuel injector cleaner added. The car ran fine for a couple of days, and then the same thing happened. I noticed that when I stepped on the throttle when starting, it would keep going. My mechanic replaced two crank sensors at $100 each, and it worked fine. Then, two days later, it stalled on my wife, but she was able to keep it going. What could still be wrong?

A: Has anyone checked the idle air control? Or the throttle position sensor? Or the engine coolant temperature sensor? A scan tool can check these at a cold start and communicate any fault codes stored in the powertrain control module memory. Any of these could cause the problem.

In addition, I think a fuel-pressure leakdown test is warranted. Any type of internal fuel leak from an injector or fuel pressure regulator is going to make a cold start difficult. And, finally, please remember that the engine has 175,000 miles on it. Poor compression, low vacuum and other wear-and-tear issues can affect cold starts.

Q: I have electrical problems with my ’96 Mercedes 320 SL. Specifically, the directional signals work infrequently or not at all — and the wiper blade worked erratically, then stopped altogether. Can you help?

A: My Alldata database pulled up an old recall bulletin, 95-1233 from January 1996, identifying a possible problem with the combination switch or its connector in the steering column. This switch controls the high/low beams, turn signals and windshield wiper.

The symptoms fit, so I’d have the dealer check to see if your vehicle was included in this recall and, if it was, whether the recall service was actually done. While it may be too late to benefit from the recall, this is still the most likely cause.