Originally Posted by OscarMike
Wrong. I get a solid 19-21 mpg @ 80mph on the interstate, where I only get 16-18 doing 55-60 on the highway.
I don't mean to cause tension, but unless your truck sits on a perfect torque curve or something, the physics of getting better mileage at a faster speed is incorrect.
Parasitic drag: when the speed is doubled, the force increases by 4 times.
For example, if you drove at 30 mph and held a 2x4 out your window lets say it took 20 lbs of force to keep it out straight. If you increased your speed to 60 mph, you would need 80 lbs of force to keep the board held out straight.
It doesn't make sense, since it takes more power to keep your truck moving at that speed. I'm sure it's driving technique. Even 4 or 6 starts and stops drop your mileage.
Unless of course the centrifugal force on your tires at a higher speed makes them balloon up and less tread touches the ground and thus causes less drag.....(i highly doubt it).
And to answer the original post. I had snow tires on my 2wd jeep grand cherokee 4.0 and the best mileage I could get (I repeatedly drove from Seattle to Spokane and back every weekend for 4 months) was 18.9 mpg. That was checked with 100 miles of mile markers, mileage compensation for slightly bigger tires size 3%. I would drive it like a granny and it just sucked the fuel.
My previous tires were almost bald street tires and I would usually get 23 mpg and sometimes 26. So I went to the tire store and bought the least aggressive tire I could that was the cheapest. It was also slightly smaller than original tires (3.5 % checked by mileage calcs and speedo checkpoints and mile markers for over 200 miles). I put those tires on and got 25.5 mpg average after that on highway.
Another thing is I could barely make it to tacoma from Spokane290 miles, without filling up. With the new less aggressive tires I filled up in North spokane and drove to Quilcene (365 miles) and then drove to work and back almost twice (100 mile or so) before having to fill back up.
There are always tradeoffs in this world, aggressive tire, less mileage. If you want better mileage on an aggressive tire, spend alot more.
sorry for long post.
Ill get off my soapbox...