by Cathy Reichow
Q. My car is using about a quart of oil in 300 miles. It has good compression and gets good gas mileage. No signs of leakage. Somebody suggested it could be a bad PCV valve. Does that sound right? It's a V-8.
A. Could be. A faulty PCV valve could allow oil to pass from the crankcase into the combustion chamber. Another common cause of oil burning is a leaking valve stem seal. These are designed to be supple and cling to the valve stem as it goes up and down. If one or more of these shrinks a bit and has become brittle it can allow oil to work itself into the combustion chamber where it burns off.
Q. When I get my oil changed they always put a "next service due" sticker on my windshield. It tells me to change my oil after another 3,000 miles. I checked my owner’s manual, which says I should change the oil and filter every 5,000 miles. Who do I believe?
A. Congratulations on having gone to the trouble of looking your question in the owner’s manual. You may have noted the manufacturer’s definition of "severe service," more stop and go driving and other factors that require more frequent oil changes. The longer interval is based on ideal conditions, i.e. steady driving in moderate temperatures. More often than not, the 3,000-mile oil/filter change is a good idea for extending the life of your vehicle. It’s inexpensive insurance; stick with it.
Q. I have a 1988 Ford F150 Pickup with duel fuel tanks. Sometimes the oil pressure gauge is very high and sometimes it is very low. Also, the fuel gauges will not come off full until the tank is below 1/4 tank. If I switch the tank from front to rear the oil pressure gauge will go up and down. I am worried that this will be a very expensive repair.
A. It sounds like you may have a problem in the ground circuit of the instrument panel. If one accessory affects another, you need to look at what they share in common. In most cases it’s usually the ground circuit.
Q. I don't put many miles on my vehicle, how often should I change my oil?
A. In our shop, we like to see our customers every 3 months or 3,000 miles, whichever comes first. An oil change is a very inexpensive protector considering the cost of a replacement engine. This also gets a technician under the hood of your vehicle to look for any future needs or problems that may be developing. You can refer to your owner's manual for the recommended maintenance schedule. Look for both "Severe Service" and "Normal Service" intervals and find what best describes your driving habits. "Severe Service" includes: driving on many short trips, driving in hot weather in stop and go traffic, driving at high speeds in hot weather, and towing a trailer. If you don't drive under any of these conditions, you could use the 6-month or 3,000 mile schedule, whichever comes first. Remember, with proper maintenance, most vehicles will go 100,000 miles or more!
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