Should I change transmission fluid?

Ask the Auto Doctor

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


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.

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?


Dear Tom: Unfortunately, gas mileage on older Chevy Colorado trucks has been low driving around town, especially if it’s a 4×4 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.

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?


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.

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?


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.

Junior Damato is an ASE-certified master technician. E-mail questions for publication to info@motor-matters.biz. Mail questions with SASE to: Motor Matters, P.O. Box 3305, Wilmington, DE 19804.


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