Q. I recently bought a 2000 Dodge Intrepid with an automatic transmission that has an "Autostick" feature and noticed a number "1" through "4" readout near the steering column. What do those numbers mean, and how am I supposed to use them? --B.F., Chicago

A. Your car has a four-speed automatic transmission that can be put in "drive'' mode all the time, but it lets you manually upshift or downshift through gears using the transmission lever. (Note the "Autostick'' name.) You'll rarely need to shift to first gear (the car always starts in second gear when the transmission is in "drive"), but downshifting from fourth gear to a lower gear helps slow the car and saves the brakes when driving down a mountain road on, say, a vacation trip. Also, some drivers like to manually downshift from the top (usually overdrive) gear to a lower gear during quick passing on highways instead of flooring the accelerator and letting the automatic pick a passing gear by itself. The number readout shows what gear you've manually selected. There now are more advanced automatic transmissions that can be left in "drive'' but allow more precise manual shifting. A few really advanced ones even have clutches, but no clutch pedal, with paddle shifters near the steering wheel rim utilized to change gears.

Q. What do you think of the 2006 Ford Focus ZX3 with a manual transmission? --H.W., Chicago area

A. The ZX3 with its 2-liter, 136-horsepower four-cylinder engine and five-speed manual transmission, is an inexpensive car that's fun to drive. But the ZX4 ST is a superior Focus with its 2.3-liter, 151-horsepower four-cylinder with that manual gearbox, sport suspension, traction control and anti-lock disc brakes.

Q. I'm interested in the Chrysler Sebring Limited convertible, but prefer the version with the soft top instead of the retractable hard top. I don't like the way the retractable hardtop model looks and it seems too complicated for long-term reliability. I also like the Pontiac G6 convertible. I know it comes only with a retractable hardtop, but that top doesn't look as complicated as the Sebring's. --L.B., Geneva

A. It's too soon to tell if the G6's standard power retractable top will be any more reliable than the Sebring convertible's optional retractable top. The Sebring Limited convertible with a power cloth top lists at $32,055, while the G6 convertible has a $29,345 base price. I've tested both and found them pleasant, mainly stylish cruisers.

Q. My 2005 GMC Yukon truck with 33,000 miles always has made a clanging sound when its automatic transmission shifts gears. Service technicians tell me the sound is normal. I think the noise indicates that some component will eventually wear out. --R.P., Dyer, Ind.

A. I would think that some part or parts would have failed long ago if the truck has had the "clanging sound" for 33,000 miles. Assuming you've had the Yukon checked and nothing was found wrong, you might drive another Yukon and see if it has the same transmission noise, although I've heard no similar noises in new General Motors trucks I've driven during the past few years.

Q. Studies have shown that few Americans check tire pressures. So nitrogen tire inflation, which is picking up speed across the country, may be the answer for improperly inflated tires that wear out faster and don't provide the performance or economy they should. Nitrogen, which makes up about 78 percent of the air we breathe, is superior for tire inflation because it diffuses through tire rubber more slowly than air -- helping tires maintain proper pressure longer than air-inflated tires. What do you think? --B.L., Chicago area

A. (Note that the writer of the above e-mail represents a manufacturer of a nitrogen tire inflation system.) I've never met anyone or heard from a reader who has nitrogen-inflated tires. Neither has veteran service technician and college auto service instructor Frank Caira Jr. of Elmwood Park's Caira Automotive, who regularly talks with his service customers. Caira notes, as you do, that most air is composed of nitrogen and that it seems to him that it might not be worth the extra money it takes it to inflate tires with nitrogen. Any readers care to comment on their nitrogen-inflated tires?

Q. I know collector cars are hot, but which are the most popular American ones? --E.H., Glenview

A. The Hagerty Hobby Survey conducted by Hagerty, a large collector car insurer, found that Chevrolet (32.6 percent) beats Ford (19.6 percent) as the most popular car make with collectors surveyed. Pontiac runs a distant third (6.1 percent), according to the survey. But most respondents also said the 1932 Ford (V-8) roadster is the car they'd most like to see brought back via a "re-make."

Car question? Send it to Dan Jedlicka, Chicago Sun-Times, 350 N. Orleans, Chicago 60654, or e-mail djedlicka@suntimes.com. Include name and hometown.