Gas mileage on 2000 Camry

In the last two or three weeks here in Boston, my gas mileage on my Camry plummeted from 25 mpg to about 14 mpg. I went to the dealer, the filters were clean, they couldn’t tell me what was wrong. They noticed my tranny and coolant fluids were very dirty so I told them to go ahead and change them out. I skipped the recommended injector cleaning process priced at $129.

I am now back to my normal mileage. Could the fluid changes have corrected the problem?


The only thing that comes to me is that the automatic transmission may not have been going into overdrive (OD) before the fluid change.

Your mileage dove because of a bad thermostat, exacerbated by cold weather. Warmer weather or fewer short trips likely had more to do with your subsequent mileage increase than the other dealer services. Your car probably has the original (or second) thermostat ($7) which is now slow to open, causing your car to run too cool -especially in the winter – as the computer sends too much fuel to the engine (warm up mode). Change your thermostat and your winter MPG will improve. I change mine every 2 years – really makes a difference.

The type of driving may have done it too. If you were stuck in traffic or had to drive really slow because of road conditions, your mileage could have gone down to cold engine city driving mileage. By some fluke, you might have driven a long time with out overdrive. If you charge your gasoline check your receipts, you might not have gone on any longer drives. If you drove so little that you bought gas after 11 days instead of 6 days, it could have made a big difference. People could have stolen a few gallons from you too. Desperate times call for desperate measures. To correct a previous post, a slow to open thermostat will cause a warmer engine. Maybe it was slow to close. A thermostat will go back and forth all the time.

Thank you. I think this may be it. The cold weather has returned and my mileage is still normal.

Hi. All of my driving is a mix of highway and city. Yikes on the gas siphoning! I guess you never know. I think it may have been related to the overdrive; a previous post indicated the fluid change may have impacted problems of not going into overdrive.

Thank you.

PS I forgot to mention that the mileage dove with very, very cold weather. However, since the fluid change, even a return of frigid weather has not negatively impacted my mileage back to 14 mpg. I’m staying between 23 and 25.

Thank you to everyone for your help. I’m still interested in more feedback if you have ideas to share. So far the overdrive connetion seems to make some sense to me.

Its also been really cold the last few weeks (live in Seacoast NH). Do you warm your car up?

no, I don’t. This is staring to seem stranger and stranger! Someone else told me the fluid change could account for the difference…

If the transmission dod not go into overdrive (4th gear), then you might have noticed that the engine was noisier than usual. This is because it would run at higher RPMs. If the Camry has a tachometer, you would have seen higher RMS than normal at highway speeds.

Cold weather could have a bigger impact in another way. Your heater makes the engine run colder. The more heat you use the more heat is taken away from the engine. Windy weather is like a bad front end alignment because it causes the car to work harder. A son’s duffel bag in the trunk isn’t too bad. Leaded gas made a comeback?

Interesting. I didn’t look at the tachometer or notice the engine noise. But I may have accidentally disengaged the overdrive button too (although I think this would have showed up on the transmission display panel.)

Thanks for sharing your thoughts. I’m beginning to wonder if this is just going to stay a mystery!