Hey everyone, I'm a newbie on this forum and want to say I greatly appreciate all of you being available to answer questions.

I have a 2007 Avalon which is still under warranty. I bought it used and it was shifting unevenly at lower speeds. I took it to the local dealership to see if there was a service bulletin. They reset the transmission and it now shifts fine. Unfortunately, the highway mileage has dropped from 30-32 mpg at 70 mph to around 27. I returned to the dealership and expressed concern. They reset the transmission a 2nd time and made sure the memory was also reset. It is not getting any better mileage now. I do not have any check engine lights. And the dealership is clueless as to what has caused the worsened fuel economy.

Has anyone else had this experience and if so, how did you correct it? Or does anyone have an idea what has caused the drop in fuel economy?

Thanks to all who respond.

Have you tried changing the spark plugs and air filter yet? Are your tires aired up to the correct pressure? Using synthetic fluids all around will gain you another 1-2 MPG or so.

The difference in mileage occurred literally from one day to the next. It was getting 30-32 mpg before it went to the dealership, after the transmission reset it now gets around 27 mpg. I fill gas at the same gas stations and nothing else has changed.

Hmmmm.... do you know how they reset the transmission? I've never heard of anyone ever "resetting" a tranny. Did they just undo the negative battery terminal and put it back on? If so, it may have reset the ECU as well. It should take a few days for the ECU to relearn the fuel trims so I would suggest give it some time. If it's been over a week with the same results then I would say go find yourself another dealer to go to.

What you're describing is not unusual. There have been many (myself included) that saw a decrease in fuel mileage after getting the 'tranny reflash' TSB performed. But all is not bad. If you'll give it a while you'll see your mileage start to go back to what it was as the computer 'relearns'.

It has nothing to do with needing a spark plug change, air filter change or tire pressure (unless yours are really low). Your computer has been reloaded with new parameters. Look under your hood for a white sticker that has this imprinted on it - TSB EG029-07. That's the TSB number that corrects poor transmission shifting.

Stick with it - the mileage will come up again.

Thanks for your help. I just returned from a road trip and what you mention appears to be happening. The mileage has already started to improve. On the outbound portion the mileage showed to be 30 mpg. The Avalon is a great car. Good mileage makes it even better. I couldn't find the sticker you mention under the hood, however. But I am quite certain the tranny was reflashed based on my converstation with the dealership.

I appreciate all who took time to respond!