As mentioned in another thread, could be winter fuel (if they have that in your area) which has a bit more ethanol in it; ethanol has less fuel energy than gasoline. I know between that and winter tires I get noticeably poorer fuel mileage in winter. Not that it's great with a VQ at any time!

 

how hard are you driving your car?

hard starts from a red light eat gas

accelerating on the highway around people eats gas

sure its fun, but you gotta play

I spend $70-80 a week on gas. Lots of driving for work on a schedule (aka speeding)

 

I've been averaging less than 18mpg since I bought the car. Did you recently change anything that could explain the mileage difference; new gas station, new oil, new tires, new brakes, new route to work, etc?

 

Wow 250 max on 15-17 gallons? I can ONLY put 14 gallons on my messed up fuel tank and get around 290-300mpg before empty.

 

my new route to work is the same distance, but much more stop and go. That being said, my hwy mileage is still horrific. I can see the needle dropping as I drive.

 

I'm averaging 20-21MPG mixed. Highway only i might manage 23MPG barely. I learned to just take it easy, but there are days I romp on it and the needle drops like a rock. These cars aren't that fuel efficient at all.

I can't complain...my other car gets like 13MPG on a good day.

 

Just out of curiosity were you getting 300m per tank before the mods. All of the mods you've added increase air intake which in turn increases fuel consumption. More air and the ecu will increase the fuel.

 

gary,

i was goin to wait till every1 got their prius's then flake so ill be the only 1 with a g35
MUHAHHAHAHAHH

 

I'm sure my area is on the winter mix of up to 10% ethanol. I just got my TS reflash and have enjoying it. My navi indicates 19.5 mpg on ave. I'll go 320-ish miles and put in about 17 gal which is about 18.5 or so.

Could be one or both 02 sensors getting a bit lazy. When they start to get old, they will not read very fast and the rich / lean intervals get longer and longer. But in general, 02 sensors make the car run rich as they wear out. But they still could be doing a decent enough job to keep the CEL light happy.

Could be low inflation of the tires, dirty maf sensor, etc..

 

My G has been averaging 16-17mpg according to my navi...

I don't drive hard at all. 40/60 city/hwy.

Even my tires are wearing out unevenly at 9400 miles.

Something isn't right. And it isn't our driving.

Heck, the G37 gets better mileage and it a 3.7 and a few more HP.

06 6mt.

 

about the same. I actually decided to not to install the spacer so that I could get the MPG situation fixed.

 

I heard NAPA auto parts stores...

 

You may want to make sure you K&Ns are clean if you haven't done that it a while.

However in my case with clean filters about a month ago my 08 xs has dropped about 1 mpg over the last two weeks with the same basic driving patterns so it may well be related to a change in fuel mix (or weather). I always buy from the same source so that has not changed.

During the last couple of weeks we have seen a change in weather so hard to state there. One thing I stress is that when you post mpg that if your car provides it post the average mph as well as that has a lot to do with your mph. In my case that has changed as well. I normally get about 21-22 with an average speed of about 30-32. Right now that average speed is down closer to 25. I haven't played with this during the same weather conditons to know exactly the effect. This average speed influence would depend of course on the mixture of speed limits and how you drive them. In my case the 5 mph drop is probably due mostly to the weather effect on myself and other drivers (law of impenetrability).

 

My G gets around 22 mpg. A huge increase from 14mpg in an F150 on 22s

 

BINGO!!!

I'm willing to bet that'll solve your problem. Have them upgrade the platinum SPs to iridiums and you should be all set