Q. How many years are tires safe to use? My wife’s car is five years old and the tires have about 20,000 miles on them. I brought the car in for service and the dealer recommended new tires. He said this was due to the original equipment tires appearing to have “dried out,” with visible cracks on the sidewalls. Is this a recommended practice; will most tires need replacement after five/six years even with low mileage use? How can someone tell when it is time to replace tires even if there is very little tread wear?

A. Generally speaking tires will dry out and crack when they get to be about six or seven years old. You could drive the car with tires older than that, but as the rubber ages the tires are prone to blow-outs and air seepage (slow leaks).

No lighter

Q. I read your column every week, thanks for all the interesting information! I went camping in my 1999 Subaru Forester, and could not light up my propane stove. (The box of wooden matches packed with the stove were damp.) So I thought, “no problem, I’ll just use the cigarette lighter in the car to light a scrap of paper!.” There was no lighter, just the socket and a dummy plastic plug! Arghh! I bought new matches from the store at the campsite, and then later bought a lighter. I don’t smoke so I never looked at the car’s lighter. Why would there be an ashtray and no lighter? I looked at a new Subaru –– it’s bigger and more plush with all kinds of bells and whistles. I also noticed several 12-volt outlets and still no cigarette lighter. Why aren’t there simple cars anymore?

A. Cars are getting more and more complicated. Some cars today have a dozen computers that constantly communicate with each other. A bigger issue is that due to the complexity and specialized tools required, some service can only be performed by new car dealerships. Perhaps this is the part of the problem with the auto industry today, maybe what the United Sates needs is a good, basic and simple $5,000 car. A word of caution about using aftermarket cigarette/cigar lighters. Many of the 12-volt outlets in today’s cars are designed for use with cell phone chargers and iPods and are not designed for high amperage use such as cigar lighters.

Rough-running Ford

Q. I have a 2004 Ford Explorer with the 4.0-liter engine. The truck has over 100,000 miles. Recently the engine started to run rough. I had it scanned and the code indicated a misfire on one cylinder. I changed spark plugs, wires and ignition coil and it still idles roughly. It runs okay at highway speeds but doesn’t have much power going up hills. It is also is worse cold than hot, do you have any suggestions?

A. A rough-running engine with a misfire can be caused by a faulty fuel injector, vacuum leaks, as well as poor engine compression. Start with a check of the basics; this should include a compression test. If the compression is determined to be okay I would then look for a vacuum leak. One common problem is the intake manifold “O” ring gaskets can develop a leak. A professional tool called a smoke machine can easily identify this type of leak.

Aging Toyota

Q. We own a 1995 Toyota Camry; it’s a 6-cylinder with an automatic transmission. Since day one we have gotten 25 miles per gallon. On long highway drives we got close to 30 mpg even going 80 mph. Now 140,000 miles later the car is only getting 20 mpg (even though I am not exceeding 60 mph). The car has the original spark plugs, but I changed the air filter and change the oil on a regular basis. Every thing seems normal. Any ideas?

A. The first place I would start is with replacing the spark plugs. As the spark plugs age they will start to misfire and waste fuel. The other issue with a 13-year-old car with 140,000 miles on it could be that its just starting to wear out. As the engine wears, it becomes less efficient and will use more gas.

Check engine light

Q. I have a 2003 Saturn Vue with 77,000 miles on it. My “check engine soon” light is on. The last time that the vehicle was at the mechanic he indicated that it was an emissions problem that would be difficult to identify. My understanding has been that you could just hook it up to a diagnostic computer and the problem could be identified. I could take it to the dealer, I’m sure they would find something to fix (they always do). Am I damaging my vehicle by continuing to drive it with the light on? My mechanic said he could reset it again (how many resets are too many?)

A. Driving with a check engine light on may not be damaging the vehicle but you are most certainly polluting the air. To repair the problem a technician will check some basic items and then hook the vehicle up to a computer scanner. The scanner will read a computer “fault” code. Once the technician has the fault code it will lead them to the area that needs repair. The code won’t necessarily give them the exact cause but will point them to the area that needs further testing. Resetting the check engine light clears the code, but it will come back on if the engine malfunctions again.

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