99.5 QX4 loss of mpg

Post by **tykeeus** » Mon Mar 10, 2008 8:41 pm

I have a 1999.5 QX4. The gas mileage has dropped off to under 17MPG on the highway. Actually closer to 16.5 MPG. I have no check engine light and all maintenance is current. Transfer case is in 2 wheel drive. I only run Chevron or Shell gas. It has about 156000 miles on it. It used to get about 18.5+ MPG on the highway about 20000 miles ago. Any ideas what to check? Are there any mods that can be done to increase MPG? This is a little frustrating with gas prices on the rise. Any help is appreciated.

Post by **timmack** » Tue Mar 11, 2008 2:28 am

were the spark plugs ever changed?

Post by **Qxxx4** » Tue Mar 11, 2008 12:46 pm

yeah change your spark plugs and more imporantly get a fresh oem air filter

weather also affects gas mileage if its really cold outside, and tire pressure obviously

mines been a little rough on gas too but according to the manual Im due for new plugs...didnt check them yet but i will make my decision when the snow goes away, alot of people have their in for 150k+ kms, mines got 105k kms.

Post by **tykeeus** » Tue Mar 11, 2008 5:38 pm

Plugs were changed 28000 miles ago with Iridium plugs. They actually helped the mileage and performance. The air cleaner was a K&N cone filter for a while, but I wasn't happy with it so went back to stock. About 2000 miles on new filter. Oil changed every 3-4000 miles. Fuel filter changed about 10000 miles ago. O2 sensors replaced about 15000 miles ago when set a code (I was hoping that was the problem). All maintenance is kept up and current. That is what is so frustrating. If it set a code, I'd fix it, but there are no signs of any problems. Is it possible the gas has gotten so bad that it has killed the mileage? I only run Chevron and Shell because all of the other brands make it run like crap and mileage drops to 12 MPG. So I rather pay the higher price per gallon then have it run crappy and get the mileage of a Suburban.

Post by **Qxxx4** » Wed Mar 12, 2008 12:18 am

that IS frustrating, your doing everything right it seems!

Post by **Infinitidood412** » Fri Mar 21, 2008 6:59 pm

dang man, under 17mpg? crap if i could GET 15mpg i would be happy...your lucky haah

Post by **tykeeus** » Fri Mar 21, 2008 7:07 pm

Mine will get as low as 12 mpg if I run any gas other than Shell or Chevron.

99.5 QX4 loss of mpg

99.5 QX4 loss of mpg

Re: 99.5 QX4 loss of mpg (tykeeus)

Re: 99.5 QX4 loss of mpg (timmack)

Re: 99.5 QX4 loss of mpg (Qxxx4)

Re: 99.5 QX4 loss of mpg (tykeeus)

Re: 99.5 QX4 loss of mpg (tykeeus)

Re: 99.5 QX4 loss of mpg (Infinitidood412)

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