Q: True or false? In our clubhouse parking lot, I came across a car that was left with the engine running, keys inside and doors locked. Security was not able to help find the owner. I mentioned this incident to friends, and someone said that if I had put something, such as a potato, in the tailpipe, the engine eventually would have shut off. Would this really have happened?

TOM: It certainly would have happened. Assuming the exhaust system is intact and not leaking, you can stop an engine by plugging up its exhaust outlet.

RAY: If the exhaust gases can't escape from the cylinders, then there's no room for the fresh gasoline and air to get in. So the engine gets starved for fuel. Now, a potato is the time-honored vegetable of choice in the fraternity community because of its wide availability, appropriate selection of sizes and tendency to stay put once placed firmly in a tailpipe. But the truth is, holding a thick rag over the end of the tailpipe would cause the engine to stall, too.

TOM: We do that as a test in the garage to see if a car has an exhaust leak. If you plug up the end of the tailpipe and the car keeps running, you know the exhaust is escaping from a leak.

RAY: There's one other consideration. When the engine dies, the key will still be in the "run" or "on" position. That means any electrical accessories turned on (lights, CD player) will continue to run off the battery. So there's a chance the battery will be dead if the car is left all day like that.

TOM: Of course, if you leave it running, it could run out of gas and THEN run the battery dead.

RAY: A car with a properly functioning cooling system won't be harmed if it sits and idles for hours.

TOM: But if the car is in a place where it's unsafe to let it idle, or if it's clearly overheating, then plug up the tailpipe and kill the engine.

Q: My '91 Buick LeSabre Custom needs replacement struts. I went to the mechanic the other day, and he asked me what type of struts I wanted. I had no idea. So he asked me if I wanted gas-charged struts, quick struts, or the Monroe Matics or Monroe Sensa-Trac. What is the difference between these?

TOM: The terms "strut" and "shock absorber" often are used interchangeably. But technically, a McPherson Strut is a shock absorber surrounded by a coil spring.

RAY: And a "quick strut" is the whole package. It includes a shock absorber, coil spring and strut mount, which houses the bearing. That's a complete McPherson strut, and it gets bolted right in and replaces everything all at once.

TOM: A quick strut is expensive. You'd pay around $400 each for them on this car, just for the parts. So you don't want that unless you need it — if your springs are shot or one is broken.

RAY: Since your mechanic didn't tell you that you need springs, let's eliminate the quick strut.

TOM: So then it's a question of whether you want gas shocks. The Monroe Sensa-Tracs are gas-filled, the Monroe Matics are not.

RAY: All shocks use oil to dampen the bouncing motion of your springs. Gas shocks normally fill the "air space," where the oil expands into, with nitrogen. Manufacturers claim nitrogen reduces foaming and bubbling of the oil during harder driving and, therefore, leads to better overall damping and handling. Since the difference between the gas shocks and the nongas shocks is about 10 bucks in your case ($120 versus $130), we'd suggest you opt for the gas shocks.