Q: When is it best to check your motor oil on your car? I've heard after the engine is hot and you should let the engine cool down for a minute or two. Is that correct?
— A.S., Hickory Hills, Ill.
A: The most accurate reading on your dipstick will be after the car has been sitting—for instance, first thing in the morning. If you check it when you are getting gas, make it the last step in your routine to allow some of the oil to return to the pan.
Q: Toyota says my 2008 Camry requires a V-rated tire. Since I very seldom exceed 130 mph when I go for groceries, can I safely downgrade to a lower speed rated tire? Also, a newspaper article said you should replace your headlight bulbs after two years because they start to dim. Is this correct?
— B.H., Center Valley, Pa.
A: We feel that you may opt for a lower speed rating, but keep some things in mind. A tire with a higher rating will usually handle better because it is designed to take more heat and harder corners. It may also ride rougher than a tire with a lower speed rating. Many stores will balk at your choice, so be firm if you make that choice. Filaments in all bulbs wear over time so it wouldn't hurt to change them occasionally, but we never have.
Q: Would it not make more sense to base oil changes on number of hours on the engine, with an outside limit of changing the oil twice a year?
— J.S., Chicago
A: Absolutely, yes. That is how they handle it with airplanes. But keeping track of how long an engine has been running, was difficult until recently. The only onboard measure of usage was the odometer. Today, carmakers like GM use time along with other inputs to compute the oil change reminder. Annual oil changes are probably fine if you don't clock over 7,500 miles in that time.
Q: I own a 2004 Honda Accord with 76,000 miles on it. I am considering trading it in on a new car. However, the passenger side electric window does not roll up and down. Honda service wants to look at it and says it probably is a bad motor that will be a few hundred dollars to replace. If I trade it in as is I assume I will get less on the trade than if everything were operating correctly. My question is, would the cost of the repair pay for itself in the higher trade in value, or is a dealer figuring that they can fix it at a "wholesale" cost?
— J.M., Skokie Ill.
A: Chances are, they won't even test the window operation at the trade in. But even if they do, it probably won't impact the amount they offer you by very much. Yes, they can fix the problem for a lot less than they would charge you. You won't recover the cost of the repair.
Q: I own a 2009 Honda CRV. Since the summer of 2011, I have had a musty odor which emits when I turn on air conditioner. This summer the odor returned whenever I turned on the air conditioner. I took it back to Honda for another oil change this summer and they said it is a mold buildup in the air conditioner and filter. They can service it, which would cost $195, but it would happen again! Have you ever heard of this, and is there something I can do to correct the problem, permanently?
— P.T., Baltimore, Md.
A: We get this question so often that we have considered saving our answer as boilerplate. In the warm, moist, dark environment of the A/C housing, microbes grow overnight. The next day, you experience this as the typical "locker room" odor for the first few minutes of driving. To eliminate the odor, you must eliminate the microbes or clean up their environment — usually both. One trick you may use is to turn off the A/C (and even turn on the heat if you can take it) during the last 10 minutes before reaching your destination. This dries out the system and impairs microbe growth. An afterblow kit, that runs the blower after your shut off the engine, does a similar job.
Q: The average miles per gallon indicator on the dashboard of my 2013 Hyundai Elantra consistently reads about two miles per gallon higher than my calculations made at the gas pump. The maintenance manager at my local dealership said that this is common and that the car indicator is the correct one. Do you think it is possible that my simple calculations of miles driven divided by gallons pumped, made several times at different gas pumps, could be wrong?
— D.C., Tavares, Fla.
A: Do you reset your onboard fuel economy every time you fill up? If you don't, some carry over may occur and affect your reading. Also, the amount of fuel in your tank can grow somewhat as the gasoline heats up and expands. Don't believe us? Have you ever seen pictures of old time gas pumps that have a glass jar on the top? The desired amount of gas was pumped into the graduated jar then gravity fed into the car. Disreputable gas station owners would pre-pump gas into the jar and let the sun expand it cheating the customer.
