MPG vs MPH

I recently drove from Manchester NH to Houlton ME. The first portion of the trip was from Manchester to Bangor. The speed limit is 65 and I had the cruise set at 73. I got 21.1 mpg. North of Bangor to Houlton the speed limit is 75 and I set the cruise at 83. For that portion I got 16.8 mpg. The terrain is relatively the same for both segments, so the only factor to impact the MPG was speed.

I have an '11 DCSB off road with 6cyl and auto tranny.

 

Haven't you ever heard that old tale that ever 5mph over 55mph you lose 1 mpg?

I guess it all depends on the vehicle and what not.

 

Yeah...above 65, the MPG really drops. My dodge Dart has the little real time gauge, and I've found that that gets best mileage between 45-55. If I set cruise to 50, I can get upwards of 50mpg. When accelerating or above 55, it drops back down to around 35. Different car, but same principle.

Think my truck gets best mpg around the same also...inlaws moved 25 miles away, and the roads there are all 45-50 straight, flat, long roads and my mpg average went up from 17.2 to about 19 since they moved. Distance hasn't changed, only average speed. They used to live where taking the freeway was the best route (70mph limit, and would go 75)

 

Is there a question? Going faster= less MPG.

 

+1

Pickups have the aerodynamics of a brick.
Takes twice the HP to go 75 as it does to go 50.

 

Drove from East Texas to Las Vegas.

21mpg cruising at 65mph
19.5mpg cruising at 67mph
17mpg cruising at 70mph

Have the 6" pro comp suspension with 35" tires.

 

I totally agree with the 45-55 being best. My ultra gauge tells me between those speeds the instant mpg is 25 to 30 on PERFECTLY FLAT roads. Any higher or lower and it drops to the usual 19-22. Unfortunately I rarely drive between 45 and 55 very long or on anything close to flat so my average is 20.7.
2.7L access cab 4x4 5 speed on 265's

 

Oddly enough my old BMW gets the same 25mpg if I drive 55 or 80. But my tacoma takes a serious nosedive in mileage if I go over 70 much. If I keep it below 70 on the highway during my normal commute I come up with an average of about 21mpg. That's with 16x8's and 265/70/16's. When I was still running steelies and 245's I got almost 22.

 

http://ecomodder.com/forum/tool-aero-rolling-resistance.php

This calculator's output is strictly a mathematical function but interesting.

 

Driving (with traffic) ~75-80 mph between Yuma and Tucson, 17.5 mpg. Empty truck.

Driving with a heavy load ~60-70 mph, but on Mexican gasoline between El Rosario and Tecate, 19.5 mpg.

 

You should never drive when you're on Mexican gas.

 

There was an episode of Top gear and they had a 5 series BMW that got better MPG at 80 than 55... Due to its 8 speed tranny...

They had a few vehicles and it was a MPG race... I'm going to look it up now

 

You sure you did your math right? I've read some stock trucks struggling to get 18 driving conservatively

 

I could see how under certain conditions the mileage might be a little better. The larger wheels would have the effect of raising the final gear ratio. And when holding a steady speed, the heavier weight of the tires and wheels would be diminished as that only comes into play when you're repeatedly accelerating.

When I took off my big tires and went back to stock diameter, I got a 2 mpg improvement, but that was for regular traffic stop and go street driving with no freeway.

Greg

 

35's on stock gears will give you much lower rpm at highway speeds than stock and out in the desert it's pretty flat for the most part so those results are possible.

Crap somebody always beats me to it haha

 

I drove a stretch of highway here where the speed limit is 85, was cruising at like 89-91 and I got 13.something MPG. These trucks are definitely not meant for cruising at high speeds. I eventually just slowed way down, at that speed it was constantly switching between 4th and 5th even on a relatively flat road.

 

There is absolutely no need to go faster than 65 mph in any truck. With these heavy vehicles the stopping distances dramatically increase and your ability to effectively control the vehicle dramatically decreases with avoidance maneuvers.

Obviously the other side effect of exceeding 65 mph as noted in this post is markedly decreased gas mileage.

 

Trying to drive 65 when the rest of traffic is going 75-80 is just as dangerous as the reduced drivability. Not to mention, if our trucks were unsafe at that speed, they'd be limited to a slower speed. I'll take my chances.

 

I've got a first gen; but, this is all relative; so, I'm joining. ha

My record, strictly taking the highway at 70mph to work everyday = 22mpg
My record, strictly taking the county roads (very few stops) at a max of 45mph; but, more often 35mph = 25mpg