I have a 2007 Nissan Altima that has recently gotten terrible gas mileage. The EPA standards allow for as low as 29 - 42 MPG in the city and somewhere in the low to high 30s on the hwy. However, my Altima is only seeing 23 to 27 mpg city and about 33 on the hwy. Note: This has only been doing this for a few months now. I used to see 34 city, about 37 on the hwy and 33 mixed.

I have ruled out the following problems:
Oil Change. - Done Correctly
Tire Pressure - Checked regularly by me and mechanics working on my car.
The type of gas - I put Shell Gasoline in it everytime. (Regular Unleaded 87 octane)
How its driven - I do the speed limit everywhere I go which is anywhere from 40mph to 55mph in city. Speed limit is driven on the Hwy.

According to the dealership the car is in perfect working order and nothing is being coded on the computer. In addition, mechanics test driving it reset the gauge on my onboard computer and claim its reading properly. (It isn't, there is at least 2 to 3 mpg difference from what i'm actually getting.) I have talked to Nissan Corp and it appears i'm the first one to call and actually complain to them about my poor fuel economy.

Has anybody else seen or heard of this??? I've tried everything and feel extremely frustrated with the poor results of my new car. Any input would be greatly appreicated.

My 2-cents:

Given the time of year, I'd guess you are running the AC more than you were a few months ago. With the civic hybrid, that can account for as much as a 4-5 MPG drop. If you can stand it, try driving a tank without the AC on.

Another thing to check is that the oil wasn't over-filled at the last change. Overfilling can cause all kinds of problems including lower FE.

-dan

FWIW, when I first bought the NAH the mpg display read 24 mpg for the first 199 miles (people test driving the car). The second day I went to fill it up and reset all gauges. My first tank averaged around 40 mpg. As time progressed, I increased tire pressure, changed to syn oil and really learned how to drive a hybrid. My FE has peaked well into the mid 40's. Check out www.thespoils.8m.com to view my photo data for winter and summer FE. Aside from a few unusual hicups with some of our Nah's the average seems to be around 36 mpg. Your car may have a bug in the software or maybe bad gas (recently here in NJ, 68 motorists were stranded after filling up at a few stations which had a high percentage of water in the fuel). Unfortunately, if it does not show as a code, the dealer wont know anything. Try to determine when something does not appear normal with the car, turn off the radio and listen for unusual sounds etc... then try to duplicate the event with a mechanic .. Good Luck

Well as I do run the a/c (here in California of course) I noticed the EV mode isn't running as much but, this problem has gotten worse in time. I've also noticed that my NAH seems to be running more and more like a regular Altima and not with out the hybrid motor in it. Like I've previously stated the oil change was correctly, and all maintance on the car is checked regularly plus my driving habits are all normal speed limit city driving. I'm still confused that i'm seeing an almost 10 mpg drop with in a few months.

Do you have your AC set for MAX or the economy mode? I am not familiar with the NAH, but am with my prius and HAH. ON the prius, if the ac temp is set to something reasonable, and NOT MAX, the engine shuts off till the cabin temp gets warm then the engine kicks on to cool it off and then shuts off.

Maybe yours is like this too, I dont know. My Prius was a 'Classic model' and didnt have an electric compressor like the Accord hybrid does.

Anyways, give the ac controls a check. Maybe raise the temp a few degrees and see what happens to the mpg.

Also, if the ac is in the Defrost mode, it runs all the time too, (least thats how the old prius did).

I am sure if all checks out okay, it has to be something easy.

You didnt mention the amount of air in the tires, but I run all my cars near max. When my mpg starts to fall, I can tell the tires need to be touched up a little. A couple psi low and it makes a difference in the mpgs.

good luck!

The two things that make my MPG fall by more then 4 digits are temperature and tires.

The first time it happened it was a tire, even though I checked them regularly and made sure they were filled with air, there ended up being a nail in one of them.

Temperature is the biggest culprit. The NAH has a sensor that shuts down the battery recharge if it thinks the battery is overheating. This often happens when the outside temperature is in the 90's or more. You will know exactly when it's occurring, because all you have to do is excellerate to over 40 miles per hour then break. If the charge needle goes way down in to the blue, your car is normal, if it barely makes it into the blue, your battery is not charging due to too much heat. try to keep the car cool on hot days. Run the AC. Keep the car in the garage or under shade when not being used. Incidentally there are also too cold temperatures (typically under 40 degrees) that effect MPG, because it takes longer to warm up the catalytic converter.

I hope its just temperature as everything will return to normal with some cooler weather.

I dont have a Altima but I suspect that is the heat taking its toll on your car, it is hot, you use the air more, the battery and engine have a bigger drain keeping the a/c going so the regen runs more to charge the battery you get less coasting regen and the a/c pulls on the engine more so, in effect you are driving somthing closer to a regular Altima than you had hoped to.

Well I do run the A/C as cold as it can get; however I do not run it at full blast I just run it to get air circulation through the car. Also, the tire pressure is at the reccomend psi (35psi) that the dealer reccomends.

I was not aware of this temperature sensor, but that does make a lot of sense because it seems the longer i'm just sitting in traffic sometimes the battery seems to drain a lot faster. And the temperatures here in So Cal has been reaching the high 90s lately so that makes a lot of sense from your prospective.

If your tires are rated above 40psi, you might try 40 I think you will see a difference there. I find at the recomended psi the car feels like the brake is on, at 40, I don't notice much of a ride difference.