Drop in MPG

Hey guys, i got a 2006 nissan xterra s with about 12,000 miles on it, and over the last few week i noiced that my MPG's drop from 16/17 to 13. I changed my driving style to see if i was using my lead foot to much but still the milage is the same. I took it into the dealer and they found nothing wrong with it. I change the oil every 3750 miles like the manual says and do all the other rotine matinence to it, any insight on how to fix this problem would be great.

Thanks

Have you checked the tire pressure? Underinflated tires can lower MPG.

Have you changed your air filter yet?

sounds like winter gas. Can you quantify "several" weeks, because winter gas has been out for a while already. 2 months in many areas.

Well i doubt its winter gas because i live in California. I noticed it Dec. 3 Tire pressure is fine, i inspect all mey vehicles every month and check tire pressure about every 2 weeks. Air filter has not been replaced, i only have 12,000 miles on the car. But i have cleaned the air filter.

have u modded your truck at all?
if I were u I'd run the codes myself.

Its all stock except for the 5 inch fog lighs i put in. The dealer said they checked the codes, but i also have a code reader so im going to check it out my self.

go to the auto store, purchase a bottle of heet, and see what that does. might improve it

21 mpg towing something, were you going 55mph? I have never gotten that good of mileage, I get 18-20 max, going up I-5 from San Fran to LA I can get 20 if I drive under 80 but usually it turns into a speed derby and I get 16 or 17 at 90+. you must be doing something right to get tha mileage.

As for the drop to 13, something is just very wrong. What part of CA do you live in? They do change our formulations for the winter, but I have not noticed any big changes myself, but come to think of it I do get a bit lower mileage these days, but not that bad.

On the way UP, to Eugene, I cruised at 70 mph, on the way back, with the trailer, I cruised at 65 mph, always staying in the slow lane, MY TIME IS FREE !!
--This pic, shows a snowless Mt. Shasta to the East !!

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--I have the 6sp. MT and use ONLY Union 76 gas, I pass cars ONLY, on requirement and I drive in the middle lane, or to the right

--I live in the S.F. North Bay--

-- --JIMBO

I like the trailer, sweet. I guess with the low RPMs at those speeds it would work. I have too much of a lead foot I guess.

My mileage dropped to around 14 this winter, but I am sure it is the gas. (I hope).

Sounds like your gas has been contaminated with ethanol.

Start looking for other gas stations that dont have that crap in it and then see what happens.