Dear Tom and Ray:

I have a 1998 Ford Expedition with 150,000 miles. My wife takes the truck in every three months to get the oil changed. During the past two oil changes, she was told that there was no oil on the dipstick. They then removed what oil was remaining in the engine, and replaced it with five new quarts. She had the oil changed about six weeks ago, and I just checked it myself before we went on a trip. The dipstick had no oil on it, and it took four quarts to get it full again. I have checked the ground where the truck is parked and there is no oil. Additionally, there is no oil, smell or smoke from the exhaust pipe. Where is the oil going, and what should I do? -- Sherd

TOM: It's going out the tailpipe, Sherd. What should you do? See if you can get the Exxon Valdez to follow you around.

RAY: Your engine's worn out, Sherd. If there's no oil under the truck, then you're burning it. If you stand near the tailpipe when your wife starts it up in the morning, you'll almost certainly see a puff of bluish smoke. It may be harder to see once you actually start driving, but it's there. Trust us.

TOM: So, you have a couple of choices. One is to install a rebuilt or used engine. If the truck otherwise is in extraordinarily good shape, and you want to keep it for another 50,000 miles, that may be a good option.

RAY: But before you do that, be sure to have your mechanic check it out from stem to stern, as if you were buying it as a used car today. You don't want to spend $3,000 on a rebuilt engine and then have the transmission fall out the next day. And with 150K on the odometer, that's a distinct possibility.

TOM: The other option is to just trade it in. With gas prices certain to trend upward as soon as the economy gets out of the pits, this may be a good time to reconsider whether your wife really needs a car as big as a cabin cruiser for her everyday needs. If not, this might be a golden opportunity to downsize. Good luck, Sherd.