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TundraGeneral discussion forum for the 2007 and later Toyota Tundra.
This is a discussion thread titled "6 MPH difference = 3 MPG!!!", within the Tundra forum, part of the Truck Forums category.
I have noticed on several 100 mile+ road trips that the tundra gets 3 mpg better when going 65 rather than 70-72. It blows my mind that such a small difference in speed and engine rpm's can have such an impact on mileage. Anyone else find this odd?
Drag increases with the square of speed. So if you double your speed, you are increasing the air resistance by a factor of 4. There are potentially some other things also going on, such as aerodynamics changing through the engine bay/over the cab/over the bed.
That is dead on. Mine is more like 64mph is peak performance for the highway. if i get over 67-69 i might as well go 75.
I cant drive 64-65 so i get screwed with 3mpg less
__________________ TUNDRA786
2007 Tundra Crew Max 4.7 TRD 4x4
285/65/18's with BF Goodrich All Terrain KO's
BedRug, Undercover, Bed Extender, Husky Liners
It's not just drag, it's also a function of rpm. Somewhere around 1800 is the sweet spot, while above 2000 it starts to get thirsty.
__________________ 07 DC SR5 TRD 4x4 5.7 TRD exhaust, 35K miles, 17 mpg city after battery disconnect reset & removing extra (charcoal?) air filter. Truxedo Lo-Pro with deck rails.
Rear Susp: ProComp ES3000 #326510 (2.25" taller than stock), 1.25" blocks plus PRG mini-pack (http://www.tundrasolutions.com/forum...and-new-truck/) gives 2.25" total lift, parking brake cable bracket spacers, wheel well height 43."
Front diff and rear ds drop; trailer hitch electrical harness tucked up above bumper.
After 20K miles swapped 305/65/18 BFG AT for 285/75/18 Toyo AT, still on stock 18x8x60 offset TRD wheels, about 1/8" clearance to sway bar. Like the extra height but miss the width. Next time either 305/70/18 or 35x12.50/18.
Added 5th 285/75/18 Toyo AT as spare. Foam pad above spare to help with bed bounce.
Bed Bounce: Stiffer E-tires are worse than stock P-metric; biggest improvement from PRG mini-pack, slight improvement from shocks and foam pad above spare. Still a stiff ride but tolerable now.
Best things about this truck: 5.7 and transmission, interior size and comfort, very quiet at high speed.
Worst things about this truck: bed bounce, no VSC in 4wd, mileage sucks above 70.
If I drove 65 on the freeway, I would get run over.......
__________________
2007 Crewmax Limited - Silver
2.5" OME Front Lift
Toytec 1" Diff Drop
1" Toytec Block rear w/Bilstein 5100 shocks
20" Ultra Mammoth Wheels
20" Moto Metal 956 (FOR SALE PM me an offer)
305/55/R20 Toyo Open Country A/T
Line-X Bed Liner
Undercover Tonneau
Console Vault
Two car seats and a box full of princess toys!
I just did a 440 mile trip yesterday from Knoxville to Atlanta and back. On the way down I was rolling around 70 on the GPS and the computer showed that I was averaging 16.3 MPG. On the way back I was running around 65 or 66 on the GPS (I am not in a hurry when I am on company time ) and when I pulled in my driveway the computer showed that I was averaging 20.1 MPG. This is by far the best fuel economy I have received out of my Tundra.
Now that I think about it when I went to Florida last year with 4 people and all our junk in the truck I averaged a little over 12MPG running 80 - 85 MPH. That trip almost made me trade it in on something else, I am glad now that I didn't.
__________________
** 2007 Tundra 4.7L 4x4 DC
** Silver Sky Metallic
** K&N Intake
** JC Whitney Nerf Bars (Black)
** And the Glock 30 next to the cup holders
Most of the state highways in South Dakota are 65mph. That is my normal speed.
Only I-90 has a 75mph limit in SD, and to the south I-80 in Nebraska is 75mph as well.
My last long trip actually surprised me when I averaged 19.0mpg on I-80 at 75mph. Then again NE is flat flat flat, and for once there was no wind to speak of.
i'm glad to see others getting similar results. I still can't believe that just a few MPH makes such a difference. I also have the 4.10 rear end so I wonder how much difference having the 4.30's would have made on similar trips?
Ditto those results here. Hauling a washer and dryer down to our lake house, at night, ~68mph, I averaged 18.7 for the trip, with the first 50 miles of that being in Dallas traffic (though for once it was moving). On the return, day driving, 74mph, nothing major in the bed, and no real traffic to speak of I averaged 17.4 for the trip. Big difference for sure. Remove that washer and dryer for the down trip, and I bet the difference in mpg is much closer to the 2.5 to 3 mpg. By my calculations, I would get to drive an extra 42 miles per fill up (20 gallons) which equals ~2.4 gallons of fuel, which equals ~$6.75 per 390 miles (20 gallons x 19.5mpg vs 20 gallons x 17.4 mpg).
Now if we look at $/time, the difference is actually pretty good.
390 miles @74 mph = ~5:16, 390 miles @68mph = 5:42, total difference of 26 minutes.
$6.75/26 minutes = ~$0.26/minute to drive 74 vs 68.
On an hour, that would be $15.60. More over, to drive 390 miles at 74, you are going to have to stop to fill up once, and that will cut that time differential some also.
All told, I guess it makes sense to slow down, the time savings are not that much (less than an hour for a full day of driving), and the dollar savings on a day long trip (10-12 hours) would pay for my meals. Thanks all for making me work this out.
__________________
Willieboy
'08 Tundra Crewmax SR5, 2x4, Pyrite, JBL
'02 Suburban LS
'91 Dodge 3/4 ton 4x4, Cummins
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6 MPH difference = 3 MPG!!!
TUNDRA786
2008 Toyota Tundra DC 2WD 5.7L V8 X-SP, Silver Sky Metallic. 
) and when I pulled in my driveway the computer showed that I was averaging 20.1 MPG. This is by far the best fuel economy I have received out of my Tundra.
Linear Mode
