ok i have a 2WD V6 and when i filled up today i calculated 11.9????WTF? im def ording a scangauge tonight but anyone know what could be causing this, i did put on a size bigger BFG's but i still shouldnt get 11.9!!! and a week ago i had my oil changed and air filter. I JUST DUNNO whats going on

 

So you put bigger tires on, so did you recalibrate the speedometer or your calculations to account for that?

Also, depending on your driving habits, your fuel mileage can go to hell.

Only take a two block drive to the quickie mart and come right back home before the engine has even warmed up? That'll get you 12 MPGs...

Otherwise, no way to tell what is going on.

 

well that might be the problem lol i just calculated how much gallons i put in divided by how many miles i drove and i got 11.9 how do i calibrate the bigger tires? i havent got the Speedo redone cuz i dunno how much that well set me back. but would goin from 255's to 265's make that big of a difference?

 

no, 255 to 265's is a negligable difference. however, when you go up from say a 32'' tire to a 35'' tire, that's where your mileage goes to ****. however, as posted earlier, very short trips are bad for mileage-- the engine is unable to reach its peak operating temps, and thus the bad mileage.

 

yeah because my school is 1 mile away, and my job is 10 miles away. its not hurting me to bad because i barely go out much cuz of either school or just tired from work so 1 full tank lasts me 2 weeks. that is driving sensibly

 

jeez mine does 13 city and like 18 highway and its turbocharged

 

well i just ordered my scanguage ima see what that will tell me, maybe i drive to fast?

 

Just to help:


255/75R16 - 649 revolutions per mile - 31.1" tall
265/75R16 - 637 revolutions per mile - 31.6" tall



255) 30 miles X 649 = 19470 revolutions

265) 30 miles X 637 = 19110 " "

Thats a little more than half a mile, and 7.39 miles difference in 400 miles. Not a big difference, but I don't know your tire size so I couldn't give you your numbers.

 

Not sure the exact revoloutions, but when I went from worn out stock 255/70/16 to new Michelin 265/70/16, it was about a 5% difference in revs per mile. Plus the new tires were wider, heavier and stickier than the stock tires, so the motor had to work harder.

I was very surprised at how much difference there was in accelleration and mileage (for the worse) with only slightly bigger tires.

Despite having lower revs on the freeway, I definitnely lost mpg changing from 255 to 265 after adjusting for speedo error.

If the OP went from 255/70 to 265/75, it would be a huge difference.

 

My 255 and 265 numbers were for reference only.

 

Here's another possibility - the tank of gas you got prior to the most recent fillup (the tank you burned to calculate the mileage) may have been crappy gas and/or you didn't fill it all the way. The pump may have shut off early. The worst mileage mine has ever gotten was on a tank of gas in Texas........12.8 on the HIGHWAY. Then again, I had the cruise set at 85 and was fighting a 50 mph headwind and the A/C was on. This was from Odessa to El Paso, I suspect the gas I got in Odessa was watered down ****. I think I *should* have gotten about 15 mpg.

The way you drive yours, 15 is about what you should get banging around town.

 

You drive all over the place. What the hell do you do that requires you to drive so much?

 

Nothing *requires* me to drive - I'm retired. I like taking road trips. I hate airports and commercial cattle cars - err - airliners. My sister lives in San Diego and I've driven out there and back twice in the past year or so - once for her wedding last spring, stayed around and house sat while they were on their honeymoon, and again to spend last winter. Last summer I took a couple trips to the east coast - school reunions.

I've put 39k miles on the truck since I bought it in 9/06.

 

i agree with dirt bike dave, once you go to bigger, wider tires, the engine has to put a little more "umph" into moving them, which uses more gas. also the crappy gas part could be true. make sure you stay away from the local gas stations and stick with well known ones, like shell, texaco, exxon and all them. although they may be more expensive, better gas=more mpg.

 

to be exact i went from Hankooks 255/65/17 to BFG's 265/70/17 i know i should see a difference in MPG but 12 MPG? it just doesnt make since to me. yes im 19 but i pay for my gas and i do my best not to hot rod around so i was hopping to see better MPG