I purchased my '06 MMH new off the lot and have since put about 5500 mi on it and have noticed the that last three tanks of gas have been very poor mileage. I was averaging about 31-32 mpg,( during the summer with a/c on) I am now getting 22-23 mpg the last three tanks. I took it in to get checked and have the oil changed and he said nothing was wrong. All he did was take it for a 10 minute drive while hooked up to his computer and it read 27.4 mpg and that was good enough for him. Well not for me, I notice that my highway economy is where I get 32-34 mpg at a constant 57 mph and even babying it in town and using as much battery as possible will only get me about 19 mpg. Most of the time after driving in town for a day the computer screen will read 14-15 mpg. I have confirmed this with filling up and duing the math, I am not using ethenol and don't do quick starts or hard acceleration. I had my oil changed after 4000 mi even though the system check said I still had 48% oil life left, but I thought that couldn't possible be correct.

 

Do you think winter gas and colder temps would have anything to do with it?

 

I don't think that would effect it 10mpg, and it hasn't been that cold here either, around 50

 

Hmm. Perhaps you should have your AC thoroughly checked. Some people noticed with an AC problem, the battery was refusing to take or use charge to protect itself, giving less power to the hybrid and EV drives (And thus drastically lowering fuel economy). However, unless I'm mistaken, you would have problems with EVing around. (If you've noticed that's the case, that you can't EV as much as you could before, this may be your problem.)

As Tom mentioned, ethonol gas content and outside temperatures could also play a major role. Have you checked your tire pressure lately? A twenty degree temperature drop, a 10% increase in Ethonol fuel content, and low tire pressure can all combine to have a pretty big impact on FE.

I'm sure others will have many useful comments as well.

 

I read that the other day about the a/c so I ran it and everything as "cool"
tire pressure is fine, and the system check is reading okay. When I press the mileage tracker on the computer and leave it on for a 15 minute tool around the town my avg fuel econ looks like mountain tops (up & down & up & down) with out hard acceleration or frequent stopping. If I let it idle at a light the avg fuel econ will slowly drop as I am sitting there.

 

Your AC should get pretty "cold"...drive around with max ac, and see if you notice that it only get "cool" or actually gets cold.

I read a post about the HV bat inverter dying out, and the driver (Camry Hybrid, but problem is the same) gets really poor mileage until the car died altogether because the HV bat wasnt charging. After replacing the inverter, he noticed his mileage was way better than before. See if you can drive around an empty partking lot (with full HV bat charge at start) and get about 2miles+.

 

Um, the ICE should shut down at the stop signs. If the car is warm and the ICE isn't shutting down, something is up. If the car is cold, both the drop in FE and the ICE running at the stop light are normal.


Get out on the freeway and set the cruise at like 60. Re-set the FE average and run for at least 3 minutes on cruise. Then re-set the FE average and do it again. Let us know what you get.

MM

 

I was usig "cool" as a pun, it does get cold

 

The car doesn't usually have a chance to get warm or build enough charge up to have the ICE turn off because I only live 4 blocks from work but have to drive because I am constanly going to jobsites and most of the drives are only 2-3 miles at a time, but at the same time if I start it and let it idle for about 10 minutes than I can run on battery alone for most of the in town traveling with the same fuel econ results.

 

I am getting better than expected FE on the highway around 33-34 mpg, it is only in town that I am getting readings of 14-15 mpg.