Q. With higher gas prices, should I sell my SUV and buy a more economical small car? --E.H., Chicago area

A. It's not a good time to do that. First, you'd get a poor trade-in because dealers are having a hard time selling SUVs. You'd pay more for a new car but expect to make up the price difference by buying less gasoline. Do the math and you'll likely see that probably wouldn't work out.

Q. I drive a large Ford diesel truck in my sales occupation and travel Midwestern states. With the considerable increase in the cost of diesel fuel, I've been made aware of a product that claims to increase fuel economy and appreciably decrease pollutants. Are you familiar with that product and does it achieve what it says it does? --L.C., Chicago area

A. I've left out the name of the product you mention because such products and other "miracle" products consistently appear when vehicle fuel prices shoot up. Such products have been proven to be worthless or virtually worthless, so don't waste your money. Before fuel injection replaced the less-efficient carburetor, there were ridiculous claims and unresearched articles about so-called miracle carburetors, such as the worthless "Fish" carburetor. It was claimed such carburetors were jointly suppressed by the auto and oil industries because it would hurt profits. Most drivers have always wanted good fuel economy, so automakers have spent huge sums and lots of research time making more efficient engines. If a cheap "miracle carburetor" existed that would have saved them lots of time and money, they would have rushed to use it because it would have given them a big competitive advantage.

Q. Our student son will be 20 years old at his next birthday, but he hasn't learned to drive, although he might be learning from his peers at college. He's serious-minded, and we think he should take lessons from a professional. How do we select a good driving school? Also, we've been satisfied with Toyota products since the early 1990s and your article about the new Toyota Corolla (April 26 AutoTimes) caught our eye. Is it a good car for our son? Our first concern is safety and lean toward a new car. --C.S., Chicago

A. The standard Corolla would be a good choice because it's fuel-stingy, has decent performance and is equipped with standard anti-lock brakes and front-side and side-curtain air bags. And you can get an optional stability/traction control system for all Corolla models except the higher-performance XRS, which I don't recommend for your son. As for driving schools, he could benefit the most from attending one of the high-performance schools advertised in car buff publications. Such schools mainly teach car control techniques, such as avoiding bad skids and situations that cause many average drivers to have accidents. Most such schools have programs for new drivers, but your son first must get a driver's license before attending one. He also should have a fair number of driving miles under his belt.

Q. I liked your recent review of Ford Motor's Lincoln MKX SUV (May 3 AutoTimes), but you didn't says what "MKX" stands for? --H.S., Chicago area

A. It stands for nothing, but probably sounded good to Ford Motor's marketing personnel. The same can be said for the Lincoln MKZ sedan, which was called the Lincoln Zephyr when introduced in 2006. That made sense because Lincoln made a slick car called the Zephyr in the late 1930s and 1940s. The 2006 Zephyr's name was changed to "MKZ" for 2007.

Q. I hear that the rare Chrysler Diablo concept car will be at RM Auction's multimillion-dollar Sports & Classic of Monterey auto auction in August in Monterey, Calif. I thought the Diablo and other Chrysler concept cars aboard the Andrea Doria sunk with that ship in the 1950s when being shipped from Europe. --N.F., Barrington

A. The sleek Diablo, which debuted at the 1958 Chicago Auto Show, was lucky. It escaped an early demise because last-minute developments prevented it from being put on the ill-fated Andrea Doria. Conceived by Virgil Exner, Chrysler's pioneering design chief, the Diablo was built at a cost of "over $250,000" -- a huge amount then. Chrysler concept cars were built in Italy in the 1950s because craftsmen there could deftly put together one-of-a-kind cars. Italy's famous Ghia coachbuilder handcrafted the Diablo on the chassis of the 1955 Chrysler 300, America's first mass-produced 300-horsepower car. RM Auctions spokesperson Terrance Lobzun said the Diablo has been in its current Chicago area owner's possession for more than 25 years. In sharp contrast, another vehicle scheduled to be at the Aug. 15 and 16 event is actor Steve McQueen's beloved 1958 GMC pickup truck.

Car question? Send it to Dan Jedlicka, Chicago Sun-Times, 350 N. Orleans, Chicago, IL 60654, or e-mail djedlicka@suntimes.com. Include name and hometown, and be sure to include a self-addressed stamped envelope to ensure a personal reply.