I have been getting horrible gas mileage lately.... I went out of town and drove 70-75 mph (or slower cause it was snowing up by Detroit)...and I only got 300 miles on a full tank. To me (read novice), it seems that it is running rich. I have a KN filter + Z tube and I use either mid grade or premium (89/93 octane). These were installed last summer and I did not notice any significant loss in mileage. Please help me out with any ideas...

Thanks,

g4ian

 

That's strange...How long was the drive, distance wise. Total mileage on car?

I usually get about 300-315 per tank and that's with stop-n-go traffic. I would say that you are hammering the gas for the sound from the z-tube, but with a year on, your over that by now...maybe

Only a few things i can think of is that you were in the snow, and possibly slowing down then accelerating as your drove through it. Possible?
Or maybe you got some bad gas on your last fill up.

 

I drove from the northeast to south carolina cruising in the 80 mph range most of the day. I averaged >25 mpg and >430 miles per tank and that was with a couple of long traffic delays. Temps were mostly 60's-70's.

In the winter I usually avg 19 mpg and the summer 23.

RJP

 

Just over 50,000 miles...(yikes!) I was driving pretty constantly slow the whole way.
On another note, my dealer is NOT mod friendly. I don't want to put back on the stock tube, but I might have to. I think I will try an ECU reset first.

Thanks,
g4ian

 

Sounds good about the reset.

Have you gone through that tank of gas already...I would try another full tank and take drive just to see.

Have you cleaned your injectors as well? 50k miles gets things kind of dirty.

 

hey man, u seem to say that you are getting 20mpg or better from full tank of gas in stop and go traffic, that is incredible..cuz i have not yet seen that..I got 400 mile out of my tank(18.5g) from chicago to columbus once or twice, but I have a very light foot and i take it easy 90% of time still i dont get more than 285(90%)-300(rarely) in 60-40 highway/city driving..thats strange, is there something infiniti service chap can do here? the refueling is killing me..

it sucks..

 

Sorry..i should have put out all of my numbers. I get about 300 - 315 per fill up. When I do fill up i usually put in about 17 gallons of gas. So that's about
17.6 - 18.5 mpg. Still not bad considering.

I just mentioned the miles per tank at first to compare his long trip to my daily commute.

 

I'm just getting my first 300+ mile tankfull as of this post. I normally get only 230 to 50. Just cracked 5,000 mi. I rarely drive any highway, and pedal "down arown town". So I'm very excited to see 300+ comm'n up on the odo. Keep in mind that I'm probably just breaking in as I've been run'n Mobil 1 since 1,500 mi. and I knew that this would be the case.

 

Well, I too have been getting close to 20 mpg (19.8 or so) and all of my driving is in city traffic, and I get that consistently anymore, 16k miles.

 

50% highway, 50% city, I get 21. 350 per take. 25K miles.

 

1500 miles on my X; I have seen a slight increase each fill, with the last tank hitting 21.38 MPG. That last # also included a lot of fun driving as I have been opening it up mucho since 1000 miles. I do 90% highway, and w/ a 75MPH limit I average 80. Even w/ those higher RPMs (3200 or so at 80), I think I could easily hit 23 MPG without all the fast starts.

 

1600 on my 05 5AT and get about 19.5. hopefully it will get better after the first oil change.

 

Clean the K/N if you havent recently. Just dont overoil it or it will foul the MAF. Check tire inflation too. Try to run 36-40 cold. The manual will probably say 32, but that is bull and way too mushy. I run 42 in my Avon 550's and get 24-25MPG consistently with 80% highway.

Also, make sure everything is tight on the intake box & tube. No loose or missing hoses/connections etc. Running a few tanks with Berryman's injector cleaner couldnt hurt either.

Lastly, use a good synthetic 5W/30 like Mobil 1 EP. Reduces frictional losses and good for 15K miles.

 

Those mileage reports are not very encouraging to me. I have two vehicles that avg. under 20 mpg. Is the TL seeing better mileage? I love the way that car looks but I don't know if I can get over the FWD.

 

My last tank of almost all city driving came to 17mpg (300 miles / 17.56 gal). Seems like the AWD G35X is getting 2mpg less than the RWD G35. Not surprising since that's what the EPA figures said on the sticker.