Q. I enjoyed your article on the new Aston Martin V8 Vantage (July 19 AutoTimes) because I have great fun driving my 2007 V8 Vantage. However, I'm concerned that Aston's high production goals for 2009 and beyond may diminish the uniqueness of its cars. Jaguar's increased production forced it to wholesale cars and subsidize leases. I feel that selling cars with a "payments" strategy removed much, if not all, of Jaguar's brand mystique. -- C.M., Chicago area

A. It's doubtful that Aston Martin will ever make nearly as many cars as Jaguar because Astons are hand-built and far more costly than mass-produced Jaguars. Aston will offer its new Rapide sedan next year, but it must do that to compete with Porsche's new upcoming sedan. Jaguar, which was owned by Ford for years, lost credibility with its recently discontinued entry X-Type sedan because that car shared parts with a European Ford model to keep costs down.

Jaguar also was criticized for making retro-styled models, despite their advanced construction. The 2009 Jaguar XF sedan (April 7 AutoTimes) and upcoming redone XJ model promise to give Jaguar a better image. Its fairly new XK sports car is a hit.

Q. Is it true that gasoline with a 10 percent ethanol content will provide less fuel economy than "straight" gasoline with no ethanol mixture? Do EPA-estimated mpg ratings on new car window stickers reflect the use of such ethanol-blended gas or the use of 100 percent gasoline? -- E.H., Chicago

A. Gasoline with a 10 percent ethanol blend is the only kind I've seen sold in the Chicago area. And -- sorry to say -- such a blend slightly reduces fuel economy. The EPA uses only "straight (100 percent) gasoline in determining its mpg ratings.

Q. I bought a 1996 Jeep Cherokee with a 190-horsepower six-cylinder engine. It runs well, although driven 118,000 miles, and has an automatic transmission, four-wheel drive and a 3.55 rear-axle ratio. However, it only gets 16 mpg on the highway. I can give it a 3.07 rear axle ratio with gears I can install for about $600. Would the installation be worth it, as far as mpg is concerned? I drive 60 miles daily six days a week. I occasionally need to engage the four-wheel-drive system in winter because I live in a rural area and must get to work. -- S.B., Peotone

A. A numerically lower axle ratio will increase fuel economy because such a ratio allows the engine to work less hard and thus use less fuel. You drive at least 360 miles a week, so the different ratio is probably worth $600 if you plan to keep the Jeep several years and gasoline remains at its current high price level. However, your Jeep was rated at 15 mpg in the city and 19 on highways, using the EPA's old rating system, which tended to give vehicles higher mpg numbers than the new system that became effective for 2008. Considering your Jeep's age, mileage and drive system, I'd say 16 mpg on the highway isn't half bad.

Q.I hear that the ideal highway speed for getting the best fuel economy is 60 mph. True? -- K.B., Northbrook

A. I've found that to be true. It's been estimated that fuel economy rapidly decreases above 60 mph. The Alliance to Save Energy says each 5 mph over 60 mph is like paying an extra 20 cents per gallon for gasoline.

Q. I've had no problems with my one-owner, garage-kept 1997 Cadillac Seville STS with 137,123 miles, but lately the "stop-engine low-pressure" warning light has come on a few times a week when I slow down or stop at a light. -- W.S., Tinley Park

A. Your car may have a warning sending light that gives a false reading. But low oil pressure can cause significant -- and very costly -- engine damage, so it's best not to take a chance. Have the oil pressure checked with a mechanical gauge to make sure there is no problem other than a malfunctioning light.