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!

See page 174 of the Owners Manual on how to reset the tire pressure sensor switch on an 07 Toyota Avalon. The reset button is on left of steering column, under dash, easy to get to...turn on ignition, hold reset button intil warning flasher light flashes 3 times. Most of the time this thing comes on when tires are rotated, when the weather gets colder, or the spare tire shows lower than 35 lbs in cold weather.

How is that even remotely related to this thread topic?

I am also new to this forum. I own a 2007 Avalon Limited and have also experienced a drop in mileage. Most of my driving is in town (5 miles to and from work daily). I took my car to the dealer today to have them check for any possible causes. They said everything checked out ok and they don't know why the decrease in mileage. They said there used to be a service bulletin out for this problem but the solution did not correct the problem and wasn't in effect any longer. I thought I'd check the internet to see if this is in ongoing problem with others. My next option will be to check with work (I work at the plant where these cars are built) to see if they have any knowledge of the problem.

it could be as simple as needing to clean the fuel injectors. the first thing i would do is get a can of BG 44k and follow the directions and add it to your fuel. don't waste money on the cheap cleaners, as they arent effective. if the ingrediants list methanol, ethanol, or any other nol, it wont do any good. get 44k or even chevron techron. i add a can every 15k miles and mileage shoots back up where it should be.

In your case I'd say your poor fuel mileage is a result of the short drive to work. After 5-miles your car is just getting up to temperature. Based on that you're usually driving in a 'cold start' state when there's more fuel being dumped, the tranny is being held in a lower gear, timing is advanced, etc.