Dear Doctor: I recently purchased a 2012 Honda Accord. The owner's manual recommends the use of gasoline that does not contain manganese-based fuel additives such as MMT. Why is MMT harmful to the car? What gas stations offer MMT-free fuel? -- Joe
Dear Joe: The MMT (methylcyclopentadienly manganese tricabonyl) additive is added to gas in the U.S. and Canada. MMT raises octane. There is no evidence of any damage to the emission or electronic oxygen sensors at this time and there have been many studies on MMT. The MMT additive is a very small amount per gallon of gas. You will have to check with gas stations in your area to see if MMT is added to that brand.
Dear Doctor: I bought a Kia Sorento AWD and I can't seem to get close to achieving the gas mileage on the sticker. In the city the best I've gotten is 12.4 mpg and 14 on the highway. I gave up my Chevy TrailBlazer, which was bigger and more comfortable and I was getting better gas mileage. Please help me. -- Kevin
Dear Kevin: Lower than advertised gas mileage complaints on new vehicles are common. The window sticker gas mileage gives the estimated averages a driver can sometimes achieve under perfect driving conditions. I use those gas mileage figures for an average number only and in most cases the actual gas mileage number that you get will be lower. All-wheel drive vehicles will get less gas mileage than vehicles with part-time 4-wheel drive or front-wheel drive. The gas mileage will sometimes increase slightly after an average 5,000 mile break-in. The use of full-synthetic oil will also help increase gas mileage.
Dear Doctor: I'm interested in the 2013 Porsche Panamera GTS. My last Porsche was a Cayenne twin-turbo, which I loved but my wife had trouble getting in and out. What can you tell me about the Panamera? -- Martin
Dear Martin: I spent a week in the 2013 Panamera GTS with AWD. It's a great-driving car on any type of road and at any speed. The design makes it easy to enter and exit. Multi-adjustable seating wraps around your body and seats four people with comfort. Front seat travel fore and aft will suit both short and long legs. The interior looks more like a jet plane cockpit, with buttons and gauges everywhere. The multi-adjustable suspension also sets transmission firmness and shift points, and opens the exhaust muffler restrictor plates. The 7-speed transmission can shift as gentle or hard as the driver wants. If you have a bucket list, then this car should be on it.
Dear Doctor: I have a 2000 Mercury Mountaineer and the "check engine" light on computer says camshaft sensor. I changed the sensor but the engine light came back on. Then I was told it could be the crankshaft sensor, as that it too could send the same signal. Do you have any idea what it might be? -- Poppi
Dear Poppi: The "check engine" light fault codes could be a faulty part sensor, multiple sensors, wiring problem or internal engine problem. The fault code does not mean the particular sensor is bad. Many car owners read the trouble codes and take it upon themselves to replace the sensor that the code reader says has the fault. Then when they come to our shop for help we usually find a wiring problem or bad ground. The other thing we do is always research the issue with technical support from the Identifix and Alldata web sites.
Dear Doctor: I have a 1987 Chevy El Camino with a 4.3-liter engine with 135,000 miles. My mechanic gave it a tune-up because it failed emissions for state inspection. After passing inspection I thought that it would be okay. The car starts and runs fine, then without warning it won't start. On two occasions, I had the car put on a flatbed to the garage only to have it start after it was dropped off. Any suggestions as to what might be causing this problem? -- George
Dear George: On older vehicles the computers cannot record and keep in memory electronic faults. I recommend the following: First, check the distributor for any rust buildup and wear. Next, connect a spark and fuel pressure tester to the vehicle and drive the car. When the engine does not start the tester will record if there's spark and fuel pressure. The most common problem with this vehicle was ignition module and pick-up failure and occasionally the ignition coil and/or connection is an issue. -- Junior Damato, Motor Matters
Junior Damato is an ASE-certified Master Technician.
E-mail questions to firstname.lastname@example.org
Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347