Toyota Tundra Forums banner
1 - 19 of 19 Posts

·
Registered
Joined
·
65 Posts
Discussion Starter · #1 ·
I took a trip from MT to MN over the 4th, doing about 75mph most of the way I got 14mpg.
Also the truck would not hold in 6th gear going up hills, it would always down shift and when traveling along on flat ground if you let off the gas then slowly step back on the gas it would almost sound like it was slipping.
When I got to MN I tried doing 70mph and stuck it on cruise control, only got 15mpg.
On the way back to MT I was bucking a head wind and only got 12.8mpg
I used to average 16mpg and now I get 14mpg no matter where I'm driving.
I do have some things done to the truck and maybe that's why it's acting this way.
I have a Road Armor bumper, 33" BFG AT's, Flowmaster exhaust and AFE replacement air filter.
Last winter I did the same trip, snowmobile in back on the way out and empty on the way back and still averaged mid 14 both ways and I had the stock tires on so the new bigger BFG's don't have much effect. I think it might be the tranny because when it is cold it doesn't want to shift into 6th. I had the dealer look at it and make sure the fluid wasn't low and they said everything looked fine but this dealers service department is a little to be desired. I also had them look at the 4wd since it would make a loud CLUNK when taking it out of 4wd and sometimes ALL the nannies would blink and be disabled on me.....they said they couldn't repeat the problem and couldn't find anything wrong. Dealerships :rolleyes:

Anyone have any thoughts?
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #3 ·
I did mention I did the same trip last winter with the stock tires and still got the same mileage.
Also my buddy has the same truck with 33" Toyo MT's and he averages 16
His wife has the same truck except in a Crew Max with 33" Toyo AT's and gets up to 18mpg.

....I don't think it's the tires
 

·
Registered
Joined
·
4,487 Posts
Here is my input... the numbers suck, but aren't bad given hills and speed maintained.

The bumper is heavy, upwards of 180 lbs. The tires are heavy, and with the extra size (both footprint as well as diameter), will add rolling resistance. The tire diameter will change your gear ratio from something that's not a 4.30 anymore. More along the lines of a 4.10 or so (I haven't done the math). The tires are also heavy, along the lines of at least 20 lbs heavier than stock, so that's an extra 80 lbs rolling resistance, taller, and wider tires that the motor is trying to push.



With all that said, it could still be the tranny, but your truck now weighs in around 6000 lbs... no longer the 5500 that it used to.

-rockstate
 

·
Registered
Joined
·
4,519 Posts
Plus did you correct mpg's for tire size? What method of mpg calculation did you use? If you have the bfg ta/ko in 275/70/18 they are ~3% difference in miles driven which gives about 3% more mpg's if you didn't do a speedo calibrator. I also believe the 1" difference in diameter does affect the trans shifts. JMO.
 

·
Premium Member
Joined
·
5,472 Posts
The avatar picture looks like you might have installed a level kit also to clear the tires. That will put more air under the truck at higher speeds also. That won't help the mileage.
 

·
Registered
Joined
·
130 Posts
The Tundra.. And most other vehicles will not hold their final gear going up a hill on cruise control.. Wind obviously plays a roll in our gas mileage.. Also, I'm pretty sure your bfg's weigh ~65lbs each, which is considerably more than the stockers.

I wouldn't be worried about it to be honest with you.

In the Tundra.. When you let off the gas to coast, then step on the gas pedal again.. The computer is trying to anticipate how much acceleration you actually want.. So its probably thinking about downshifting into 5th, but decides you don't want it and stays, or goes back to 6th. It may even jump down into 5th for a split second and return to 6th.

I maintain 16.2-16.5 combined city/highway.. I use Cruise Control quite a bit and go just under 70mph (highway of course) and drop 1-2 mph going up hill.. That's the only way to maintain a decent avg mpg with this vehicle.

BTW.. I've got a 5.7 crewmax 4x4, 3/1 leveling kit, front brush guard, tube steps, ARE bed cover, k&n drop in, stock trd wheels and bfg's (for now) and about 150-200lbs of unnecessary weight.

Jake
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #8 ·
Yeah you guys got a point plus I believe they use a different gas in the winter and with colder temps you tend to get poorer gas mileage so even though I was getting 14mpg then I probably won't this winter. :(

I didn't buy this truck for gas mileage but it is a little irritating when you already have crappy mileage to begin with then lose even more.

And YES I do have a leveling kit which with the bumper and a strong head wind does not make for a good time.
 

·
Registered
Joined
·
130 Posts
Lmao.. She IS pregnant by the way! Our first.

She's not 150lbs Yet!! With all the food and drinks she brings to work, that may add up to it!
 

·
Registered
Joined
·
7,461 Posts
oh my...not another "my truck gets XX mpg thread".....
 

·
Premium Member
Joined
·
1,530 Posts
I think it might be the tranny because when it is cold it doesn't want to shift into 6th.
Anyone have any thoughts?
That is normal :) It helps everything warm up quicker. Toyota's (and many other manufacturer's) have been doing it for many years now.
 

·
Registered
Joined
·
859 Posts
60 mph. Stock wheels. Driving style is everything. Anyway, what does it really matter? When you break it down, the savings between running at 17 mpg and 14 mpg over a year won't even buy you a daily latte.

Lets say 15k per year, average of 14mpg = 1071 gallons. 17mpg (and you will be truly unlikely to average that over the whole year - 882 gallons

1071-882 = 189 extra gallons. Divided by 365 = .51 gallons a day. Times 2.50 (roughly the current price of gas around here, actually its as low as 2.37 as of 7/6/2010) = $1.30 a day.

Better gas mileage is possible. You CAN get 20. Not in yours now you added all that stuff, but in astock. But it aint worth the effort.
 

·
The M.F.I.C.
Joined
·
3,762 Posts
^^^ Excellent point Frag, tried to throw some points at ya, but can't yet
 

·
Registered
Joined
·
3,696 Posts
I towed a borrowed pop up camper and an additional 800 lbs of camping gear from Farmington (5300 ft) to Pagosa Springs (about 8500 ft), total 160 miles one way all up hill. I filled up in Farmington at drove with the trailer to the RV park then over Wolf Creek Pass and up to a lake in bfe. Filled up in Pagosa for the trip home, 14.5mpg and 14.1 on the way home. The truck didn't even notice the 3500+lbs behind it. I pulled the same load with my 06 Ram 2years ago and got 12.

I am impressed, today I drove 300 miles and got 17.85. Not bad for either trip considering my lead foot and the ac was on.
 

·
Premium Member
Joined
·
352 Posts
now you got the fragman going,, hold on its gonna get sticky...
 

·
Registered
Joined
·
65 Posts
Discussion Starter · #18 ·
Just an update, I brought the truck in to the dealership along with a print out of the TSB regarding the front differential problem.....parts are being ordered.
Guess it wasn't my tires...or the bumper...or the lift.
 

·
Premium Member
Joined
·
1,261 Posts
Just an update, I brought the truck in to the dealership along with a print out of the TSB regarding the front differential problem.....parts are being ordered.
Guess it wasn't my tires...or the bumper...or the lift.
Got mine done and got 1.5mpg back... of course that was before I switched out the tires/wheels, so lost it again. But still... for about 6+ months, I was getting 14mpg when I was used to 16mpg+. Of course now I'm at 14.2mpg, but I've got a LOT of mods on this thing... 2.5" higher up front (1.5" in the back) and a truck that is now 6280 lbs in weight (almost 600lbs heavier than when I got it).

Also, a good rule of thumb to remember is that every 1lb of rolling weight (i.e. added tire/wheel/rotor) = roughly 5lbs of real-world added weight. So, if your stock tires/rims weighed 60 lbs each, and the new ones are 100 lbs each, than you're looking at 40lbs x 4 = 160 rolling lbs. 160 x 5 = 800 lbs of real-world added weight. That can kill both your mileage and handling characteristics (if your truck is lifted), so keep that in mind when calculating mpg.
 
1 - 19 of 19 Posts
Top