Dear Car Talk:

I have a 2005 Pontiac Vibe with 63,000 miles on it. I bought it new and have had regular maintenance performed at the place of purchase. I recently took it in for an oil change, and was told that there is oil on top of the motor. They said the manifold needs to be replaced, for about $435. I took it to an independent garage that we have gone to for years, and they said it is the head gasket, and is about $1,500-$2,000 to repair.

Why would this happen to my car? I am a 78-year-old woman who does not hot-rod her car. Who should I believe? It is not dripping oil on my garage floor. The mechanic at the independent garage said to keep an eye on the oil and add when needed. Help! -- Ann



I'd be tempted to take the advice of your independent mechanic, Ann, and just keep an eye on your oil level and top it up when necessary.

You don't say how often you've had to add oil so far. That's a key piece of information. If you have to add a quart every 1,500 miles, then there's no urgency at all, and you can just keep an eye on it -- perhaps for years. If you're adding a quart every 500 miles, then some more investigation would make sense.

So start by monitoring your oil use. Have the guy at the independent shop show you how to check the oil. You'd do it in the morning, before you drive the car. Check it once a week and see how many miles you drive before it gets down to the "ADD" line on the dipstick (meaning you're down a quart).

If it is losing a quart in less than 500 miles, start by getting the engine steam-cleaned. Between the wind blowing in through the grille and the general grimy disgustingness of engines, it can be hard to tell exactly where a leak is originating. By cleaning the engine and then checking the area again a week or so later, it can be a lot easier to see what's actually leaking. If your mechanic has a dye system, he can put a special dye in the oil, and then look for the leak with a blacklight. If not, he can just do his best to trace it to its source.

If I had to take a wild guess, I would say the guy who suggested it's the head gasket is more likely to be right. We see a lot of leaky head gaskets on these cars.

I also like his advice to watch and wait. After all, at this age (the car's, not yours, Ann) there's no sense in doing anything rash, especially if your garage floor isn't even getting dirty yet.