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Should I Change the Automatic Transmission Fluid?

By Junior Damato, September 29th, 2018

strong>Dear Doctor: The transmission fluid has never been changed on my 2006 Honda Odyssey with 145,000 mile. There are no problems with the transmission. Should I change the transmission fluid? Or, do a transmission flush? Bob

Manufacturer photo: 2006 Honda Odyssey
Manufacturer photo: 2006 Honda Odyssey

strong>Dear Bob: I suggest you drain the fluid (about 3 to 4 quarts will drain out, not the entire 12 to 13 quarts). The new fluid you add will mix in with the older fluid, verses a flush that changes 99 percent of the fluid. Doing a drain-and-fill will not shock the transmission. You can perform a drain-and-fill over the next three oil changes. Use only the Honda-factory fluid.

strong>Dear Doctor: I purchased a used 2005 Chevy Colorado pickup truck with the 2.8-liter four-cylinder and automatic transmission with 77,400 miles. Not knowing its history I changed the basics -- engine air filter; engine oil (5w30 synthetic Castrol Edge High Mileage); synthetic transmission fluid; rear-axle grease, spark plugs, and gas cap. When the "check engine" light came on, I replaced the downstream O2 sensor, and the upstream manifold O2 sensor. I was expecting city gas mileage to be around 17-18 mpg, but instead I'm only getting 12-13 mpg. I use 93 octane gasoline and Seafoam engine and injector cleaner regularly. The higher octane has no effect on the mileage. There are no fuel leaks and the transmission does not slip. Can you tell me why a four-cylinder engine only gets 12-13 mpg? Tom

strong>Dear Tom: Unfortunately, gas mileage on older Chevy Colorado trucks has been low driving around town, especially if it's a 4x4 configuration pickup. You replaced all the correct parts, using the correct fluids. If there were an engine system malfunction, then the computer would set a check engine light.

strong>Dear Doctor: I purchased a used 2014 Jeep Wrangler Unlimited Polar Edition several months ago with 21,000 miles. Recently, after starting the engine, the ABS light and the stability control lights came on. After pulling out of my driveway, the lights go out. But, when returning home and pulling into the driveway apron, these lights turn on again. Fortunately, I did buy an extended warranty for this vehicle. Any thoughts? Vinnie

strong>Dear Vinnie: The computer will hold the trouble code in memory, even when the lights are out. I would take a close look at the ABS sensor wire going to all wheels; it sounds to me like a wire connector, not a faulty ABS sensor. I see a lot of these Jeeps that have been raised up, or used for off-roading where the ABS wire has been stretched. Your technician will be able to identify the wheel that has the sensor fault.

strong>Dear Doctor: I own a 2009 Toyota Tacoma 2WD with the four-cylinder engine. For the past year the radio has been cutting out. Sometimes it comes back on immediately, and other times it takes a few minutes. The dealer said I may need a new radio, costing $1,200 plus labor. What would you do? Bill

strong>Dear Bill: I recommend installing a good aftermarket radio for one-quarter the price of a new radio. Today's aftermarket radios are plug-and-play units that include the wire adapters and radio face plates, which are capable of being controlled through the steering wheels controls, if applicable.

strong>Dear Doctor: My 1997 Ford Thunderbird has 191,000 miles. Since I last put gas in it (I always zero out the mileage counter), I've driven the car nearly 150 miles and the gas gauge hasn't moved below the "F" mark. Prior to this time I hadn't notice any issue with the gauge. What should I do? John

strong>Dear John: Most likely there is a problem with the float in the gas tank. The technician can try to read the fuel-level sender with the scan tool if the car has software, or check the actual OHM resistance and wire color at the tank. This information is available at Alldata and Identifix.

Big Drop in Fuel Mileage: Get Engine Test


Big Drop in Fuel Mileage: Get Engine Test

strong>Dear Doctor: I have a 2014 Ford F-150 with the EcoBoost engine. The dealership cannot tell me why my gas mileage is at 9 mpg. It was 24 mpg when I purchased it. Can you help me out? Gerald

Gas Mileage Misread: Fuel System Needs Attention


Gas Mileage Misread: Fuel System Needs Attention

strong>Dear Doctor: I own a 2006 Ram 2500. The mileage calculator says I'm getting 30 miles per gallon in fuel economy, but I'm actually getting about 20 mpg. What should I do? Mark

Car Shakes at Idle: Check for Multiple Fault Codes


Car Shakes at Idle: Check for Multiple Fault Codes

strong>Dear Doctor: My 2009 Toyota Camry with 199,600 miles has a check engine light showing the codes P0101 and P0170. I have already replaced the MAF sensor, PCV valve, throttle body, the car's computer, O2 sensors, cam sensor, crank sensor, fuel pump, injectors, and fuel pressure regulator. I also checked for multiple vacuum or air leaks, and the cabin air filter, spark plugs, alternator, and battery have all been checked over the course of a year. Now the car has both codes showing consistently and it shakes at idle. What should we do? Cheyenne

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