POOR Gas Mileage - Ideas????

[3 DOGS]

My gas mileage has dropped - BAD!!!
When I bought the truck (used 39,000 in June) I was getting 18/20.
I then took it in for an oil change and check up (at the dealer) and my mileage went down a little to 16/19-20 - nothing too bad but a definate differance that I noticed.
Then I got my new tires - 265/75/16 - up from 265/70/16 mileage dropped to 16/18 - expected I guess.
I traveled out to Colorado and ONLY got 15-17 on the interstate :smileeek: across Nebraska. I figured it was just the strong cross wind. Still very unacceptable though.
In Colorado I got 19/21+ :wings: !! I was amazed. This included traveling from Colorado Springs to the White River National Forrest.
Driving back to Nebraska I dropped to 16/19 again. And now I am getting 15/18
I have tried fuel injector cleaner, right foot control and everything else but my mileage keeps dropping.
I knew with the tires it'd go down but the rest of the info I've given doesn't add up to the mileage dropping so badly.
I use 87 octane gas. NO ETHANOL!
Any ideas why?? Any ways to help correct the problem? I don't have nor do I want a K&N system. I am trying to keep from going overboard with "bolt on" this and "modified that".
I can live with 16/18 or better - this 15/17 and less is almost as bad as the Chevy I traded in for the Taco.
HELP!!!!

 

[Ursidae69]

With each new mod, mine drops more. I average 16mpg. I wouldn't think that your tire change would have that much of an effect.

 

[flyingwil]

I have noticed that mine changes too, I fluff it off to summer and winter gases. Also with the larger tires, as small as a 2 psi change I notice a change. Try this... try 35 psi for one tank (I did this to prevent the cupping), then go down to 32 psi for the next tank... you will see a change in MPG. I also notice that windows up/down makes a difference too.

Start mechanically, air filter clean, MAF cleaned, and work your way on down, fuel filter, ect.. That might have something to do with your performance.

 

[bigreen505]

... then move down to the O2 sensor.

 

[Ric]

I use http://www.seafoamsales.com/ works great, really cleans the engine out.

 

[erin]

I dropped about 1 1/2 mpg with the new tires, but after regear, got it back. But when I took off the air dam and added a winch bumper, I have now lost about 2 mpg. Like Chuck said, the more you add, the more you lose. Your air pressure will definetely help though.

 

[Mlachica]

In addition to what's been said...

Has your driving style changed? cruising speed?

have you kept up with your maintenance? Such as your air filter, fuel filter, spark plugs?

 

[Nullifier]

Wieght has a huge efect. Were you loaded with a bunch of stuff? even 250lbs can really make a difference in the mountains.

 

[3 DOGS]

I plan on the fuel filter next and I guess the O2 sensor.
As far as weight I had more gear/weight in Colorado and got 21+ mpg - just really odd.
As far as the a/c or windows no significant changes when I checked the mileage before.
I just don't know. I am going in for the oil change and tire rotation so I will have them re-balance the tires and try a different air pressure.
Everything else is stock - or the way I bought it - except for the gas mileage going DOWN.
Thanks for the input

 

[Grim Reaper]

Did you take into account that the larger tires makes your odometer run slow?:ylsmoke:

 

[chet]

style of tires makes a huge difference as well. if you went to MT's they will suck more than an AT will

 

[bigreen505]

I think you really need to check out tire pressure as a culprit. In Colorado you had better gas mileage, and unless you let some air out of your tires, you were running higher air pressure due to the increase in altitude. This is the same reason that all your toiletries looked like they were going to explode when you got here ("hey, watch where you are pointing that sunscreen!"). Go add 5-7 psi to your tires and see if that affects gas mileage or not.

 

[BrandX]

you may want to try the o2 sensor last. you either have 4(v6) or 2(4cylinder) and some of them are $300.

 

[Cackalak Han]

Over 3 years later?

Anyway, I'd probably chalk it up as a combo of winter gas, higher elevation, and/or MPG calculations.