Question: I would like your opinion on something. Back in May of this year I took my car to my local mechanic to get an oil change and he said that the bolt to the oil pan was loose, so he put another one in. After a few days I noticed oil spots on the ground under the car. I took it back in and my mechanic told me that he would have to put in a new oil pan, as it was worn. Funny thing, the oil never did leak all those other times that I had my oil changed there until he put the new bolt in. I think he should have given me some kind of discount since it had been less than a month since the oil was changed and I feel that it was his fault, since it had never leaked before he worked on it. What do you think?Answer: It sounds like the drain plug threads in your oil pan became worn to the point of stripping. When this happens the plug spins as it's being tightened, rather than snugging up tight. How did the threads become like this? It's possible the plug had been over-tightened one or more times in the past, or simply wore out the pan's threads after perhaps 30 or more oil changes. Every important nut and bolt on a vehicle has a torque specification (how tight it should be) and many folks, myself included, likely exceed this if extra time isn't taken to use a torque wrench when assembling things. The thought of a drain plug coming loose and falling out, or a wheel falling off certainly sends shivers down the spine of every mechanic, and there's always the urge to tighten such fasteners just a bit extra.If your mechanic is the only person who has ever removed/replaced the drain plug, and there haven't yet been that many oil changes, he should assume responsibility. If there have been other chefs in the kitchen, or the oil has been changed dozens of times, he's off the hook. Drain plugs typically use a plastic or soft-metal gasket, and it's a good idea to renew this part each, or maybe every other time the plug is removed. In addition to preventing oil seepage, the gasket compresses slightly— like a cushion, reducing the chance of pan and plug thread damage.What's the fix, now that the threads are damaged? An oversized, self-threading plug can be tried, but they often don't seal very well, or will begin to strip again sometime in the future. Renewing the oil pan is the textbook solution, but the cost of the part and labor to install it can be excessive. I've had good luck with rubber/expanding drain plugs. They seal well, but should be replaced perhaps every third oil change or so, as the rubber deteriorates with time and use. If I wasn't planning to keep the car forever, this extra five bucks every so often makes more sense than renewing the oil pan.Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose. E-mail under-the-hoodearthlink.net. He cannot make personal replies.