Dec. 28--Q: The gas in our area changes from summer blend to winter blend. Since the winter blend became available, I noticed a drop of about 2 miles per gallon on my new vehicle. My guess is the change in gas, however, my wife thinks it is the way I drive. Can you help me solve this debate? My marriage might be at stake.
-- B.H., Arlington Heights, Ill.
A: Your hunch is correct. When it is cold out, gasoline does not vaporize as readily as when it is warm. The winter blend has a higher Reid vapor pressure than summer gas. Some drivers have written in to ask why their engines run poorly on warm spring days, and the cause is the same. The high RVP causes drivability issues.
Q: What is the best way to clean your vehicle windows, so they are streak-free? What type of towels do the guys at the car wash use to get your vehicle dry and spot-free so quickly?
-- M.N., Chicago
A: Almost everyone is switching to microfiber towels. Once you try them, you will switch too. Believe it or not, automotive glass cleaners are formulated differently than household cleaners that evaporate quickly. If you want to make your own cleaner, mix 2 tablespoons of white vinegar with 2 cups of water. Avoid any recipe that contains ammonia, as it may damage window tint.
Q: Is it still possible to roll back the recorded miles on these electronic, digital odometers as it was possible on older, mechanical odometers?
-- J.D., La Grange Park, Ill.
A: Looking to get more for your old jalopy when you put that for-sale sign in the window, huh? You better not. It is illegal. Of course, bad guys will still do it. Like any digital device, the odometer can be hacked and occasionally is. With the right equipment, the mileage can be changed. In fact, it must be changed if a new instrument panel is installed. Before driving away, the actual mileage must be entered into the panel.
Q: Why does one need an eight-speed dual-clutch automatic transmission? A fair number of cars now offer this feature, but it seems to me to be a lot of complication and hence a potential for malfunctions and big repair bills. I have a Nissan Altima with a constantly variable transmission, which I believe is much simpler, gives excellent performance, economy and the smoothness of a Buick Dynaflow. (Remember those? I owned one.) I can see an eight-speed for the racecourse but not for creeping along during rush hour, driving around town or even interstate cruising. Your thoughts?
-- R.E., La Grange, Ill.
A: That eight-speed (or nine-speed or 10-speed or X-speed) transmission and the constantly variable transmission (CVT) in your Altima are designed to achieve the same goal: fuel economy. Engines have a sweet spot where they run most efficiently. If the perfect RPM can be achieved quickly and then stay put, the car gets its best gas mileage. CVTs have come a long way since their introduction in the 1980s when their belts could not handle much of a load without failing.
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