strong>Dear Doctor: I fill my vehicle's gas tank every week during my lunch break. I took my co-worker with me last week and he said not to overfill the gas tank. When the nozzle clicks stop do not put any more gas in. I told him I could usually get another gallon in. He said it's not good, but could not explain why. Is this true? Ray
strong>Dear Ray: Yes, it's true. When you overfill the gas tank you take a chance of damaging the EVAP system in the vehicle. All late model vehicles have a charcoal canister that can be damaged when the gas tank is overfilled. Remember the gas will expand with heat. You also never want to buy gas when the tank truck is refilling the underground tanks at the gas station. Always buy gas in the early morning or at dusk. There is less vapor loss during these hours.
strong>Dear Doctor: I recently had my 2003 Buick LeSabre serviced at 96,000 miles, including oil change, tune-up, transmission fluid change and replacement of two motor mounts. Now, after this service the engine vibrates at idle. The mechanic replaced the mounts with another brand (neither replacements were GM) but the problem remains. Three individuals in the shop checked and could not find the cause. The tune-up and other work, along with the vibration dampener, were rechecked and found to be OK. Do you have any suggestions? Frank
strong>Dear Frank: The first step is to have the technician pry the engine in any direction while you are sitting in the car and see if the vibration changes or goes away. This is the way we check engine-related vibrations. A vibration at idle can also be related to the wrong serpentine belt and or metal-to-metal contact in the exhaust. As for the aftermarket engine mount, the technician will need to make sure it matches the original. Some engine mounts are liquid filled and some aftermarket engine mounts lack quality and are not liquid filled.
strong>Dear Doctor: I recently had my 1999 Nissan Pathfinder SErviced by a mechanic friend of mine. He changed the spark plugs and wires and did an oil change. Ever since then my service engine light has been going on and off. What could be the cause? Jim
strong>Dear Jim: Anytime the check engine or service engine lights comes on, it indicates a signal or value that the computer cannot calculate. Before anyone can tell you what is causing the problem, the computer code needs to be retrieved. One of the biggest problems I see is that some technicians will get the fault code and just replace the parts in the system and not actually check the system before the parts are replaced. Just because there is a fault code does not mean the sensor in the circuit has failed.
strong>Dear Doctor: I am researching online the many gas saving devices. They all make claims on substantial gas mileage increase. Have you tried any of these devises? Fred
strong>Dear Fred: Do not buy this junk online or through TV infomercials. If any of these devices worked the companies would give them out to automotive journalists to test and report on.
strong>Dear Doctor: Can you tell me about the 2011 Mercedes CL550 4Matic? I recently visited the local Mercedes dealer and was very impressed with the car. Harold
strong>Dear Harold: I spent four days in the CL550 coupe 4Matic. As soon as you open the door you can feel the quality. The twin turbo V-8 cranks out 429 horsepower via a 7-speed automatic, making this car amazing. Mercedes has taken a V-8 engine, put twin turbos on this all-wheel-drive coupe and made a fabulous engine that has more power than any one would ever want: zero-to-60 mph in 4.8 seconds. Unlike other vehicles in this class the leather and seat comfort are beyond imagination. Gas mileage is at 15-mpg city, 23-mpg highway. Our test car had a base price of $113,150. With all the options or sticker price is $127,075. Yes, this is a lot of money for any vehicle.
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