lesz

I found the second of those two links to be especially informative, and I think it gives a rather comprehensive summary of the several reasons why gas mileage goes down during the winter.

Those who drive lots of short trips are likely to see more significant drops in mpg. If you monitor the real time fuel consumption in the information display, you will see that mpg takes an especially big hit during the time it takes for the vehicle to get to normal operating temperature. When there is extreme cold, it takes significantly longer for the engine to reach those normal operating temperatures, and those who drive lots of short trips can end up shutting down the engine before it is even completely warmed up. Thus, much of their driving is done when the engine is operating at very inefficient levels.

Most of my driving is done on country roads, and I do very little stop-and-go driving. During the summer, driving in these conditions, my typical actually calculated mpg is between 20 and 21 mpg. This winter has been brutal. About half of the days have had below 0 actual temperatures with a number of days in the -20 to-25 degree range. My mpg with the GX has dropped to between 16 and 17 mpg, but I'm confident that it will go back to the 20-21 mpg range when spring arrives.

With regard to "winter blend" gasoline, differences in mpg resulting from it are likely to effect only those living and buying gas in major metropolitan areas because the law requires "summer blend" only in those major metropolitan areas, and the rest of us are getting "winter blend" gasoline throughout the year.

NR04

To the OP, did you get new tires?

When I purchased my 2006 GX last year, it came with Michelin LTX tires. Light, soft and fuel friendly tires. I average about 16 MPG overall.

Since I bought the truck for expedition purposes, I quickly replaced the tires with more aggressive thread and stronger side walls (LT instead of P). Both additional thread and weight lowed my MPG by 3.

Another major factor to consider is speed. Our trucks are not very aerodynamic. You can see a drastic difference in MPG when traveling at different speeds on the freeway. I lose about 2 MPG if I average 75MPH versus 65MPH. My other car is an Audi A6, which has very low wind resistance, and I hardly notice a difference in MPG between those freeway speeds.

ALAN553

Coincidentally this article appeared in USA Today yesterday.
http://usat.ly/1fPPeED

fantic

I have been kind of disappointed in the fuel mileage of our GX since we have had it. We average about 16 mpg. I have a Yukon XL Denali that weighs 1000 lbs more that gets the same mileage or better.

RCsGX

I have been too. I got better gas mileage in my lifted '06 Tundra DC w/ 33" M/T tires and it had the same engine as the GX. I even got better gas mileage out of my CTS-V and I drove that like I had a lead foot. I guess the only good thing is no matter how I drive the GX (all city), I average the same MPGs (11-12MPG)...that still doesn't make sense to me.

tecman

Yes I have the 460 and I also carry about 200+pounds in the back, thanks for the reason I should get worse MPG. I did not know there was a significant change in weight.

RCsGX

GX470 curb weight
4,871lbs.

GX460 curb weight
5,305lbs.
then add the 200lbs.+ you carry in the back.

tecman

Thanks for the info!

MADUFF3

I know this is old but geez.. when mileage drops off in a not so old otherwise well maintained vehicle.. Check all the variables, no problems or lights on the dash... if all that is good... replace your O2 sensors,they help compensate for optimum fuel mixture if its off so could be that..

Rdecode

I've also noticed bad mileage last times on my GX470 (2006), I use ELM327 Bluetooth OBD2 adapter + Torques Pro to monitor sensors.
Could somebody explain which sensors to monitor with regard of bad mileage and what are their normal values to compare.

So, far no error DTC codes, no "check engine" etc, however noticed 15-20% low mileage, especially in the city driving.

Thanks.

ALAN553

Aging O2 sensors can affect gas mileage. Not bad enough to set off a trouble code...but certainly no working up to new specs

http://www.mpgenhance.com/oxygensensor.html

Matsui

I experienced a sudden similar drop in MPG about two years ago. Everything seems to be in good shape, but I haven't done anything with the oxygen sensors yet. I'm at 150k and I plan to change these soon to see what happens - they are kind of pricy though. Some here have reported improvement after changing them + another sensor which I can't recall at the moment.

Htony

Cold weather can drop tire pressures 3 psi or more.

ALAN553

1lb for every 10 degrees..