Sure I can't guarantee the grade of the road. I chose this road becuase it flat to me and it's a place where I can set the cruise control at 50mph for 19miles and not worry about stop signs, street lights, viadocks, traffic in front of me, people turning on roads slowing me down which causes me to touch the accelerator/break pedal. it's 20 straight minutes in MDS mode with the cruise control turned on and i'm resetting the mpg every mile. But, I don't feel it's miracle mileage. I believe if someone duplicates this test, they will see similar results to my data. My Low number for my data is 23.4mpg and a high with 27.0mpg. My median number is about 25mpg. I only record the highest data point for the last 5 miles of driving because that's where the mpg meter will start to plateau.

How would you suggest I hand calculate a 19mile test to validate the accuracy of the mpg meter in the truck?

I would have to fill-up the tank to full, drive 19 miles on the road I test on and refill the tank. Except there is no gas station at either end of the road.

I'm not claiming this is my regular gas mileage for a tank of gas. Im trying to provide proof where the mpg meter will plateau at the fastest speed possible while staying in 4 cylinder mode. So far my data is telling me you get an average of 25mpg in 4 cylinder mode going 50mph.

 

Actually since that metric it's over 32 mpg (canadian gallon). I have got around 29 mpg (a short run till a hill)with mine so I believe you. Anytime I have checked the computer to working it out myself the computer has always been within .5 mpg.

 

I can believe it some. You must be in western Iowa. I have been out that way when I worked for a power company building new line in mid to western Iowa, and he is right. It is FLAT and you don't see much but corn fields. I got 19-20 once, when my truck was new, and was on a 4 lane highway and cruise set at 65. and the road was fairly flat.

 

Esat to believe, I routinely get 22-23 MPG on the freeway and my best is 26.7MPG. My picture of that is as shakey as yours I did it at a steady 65MPH and I am just a tad higher in elevation than you.

 

Also remember a strong tail wind will make a big difference. Our trucks are more suseptable to drag because of the big surface area of our trucks in comparison to a car.

 

I wish! Highest I have seen mine go so far is 14.9L/100km and thats only been since the weather got nicer. Most of the winter I was sitting around 19-21L/100km.

 

It seems to be very temperature dependent as my mileage went down with the temperatures in the last couple of days.

 

Is it really that hard to believe that a 2.8L engine can achieve 25MPG?
Yesterdays Photo

 

Size of the engine is not the deciding factor for fuel economy.

Aerodynamics and weight play a significant factor among others.

For example, my 7.0L motor routinely offers over 28mpg on the highway because it's in a Vette that is basically a wedge and only weigh's 3400lbs with me in it. I'd guarantee it wouldn't even muster 20mph with the same engine in our trucks.
To further the point, ironically the 6.2 motor in a C6 Vette is rated at 16/26 to a Honda S2000 with its 2.2L motor which can't even muster half the power is at 18/25.
On youtube, Jeremy Clarkson proved a BMW M3 with a V8 can get same/better gas mileage in certain situations that of a Prius. Don't believe me, do a search on Youtube for 'm3 prius top gear'.

Contrary to widely held belief, size doesn't matter much at all.
Weight, aerodynamics, engine efficiency and driving style have more to do with mpg than size of the engine.

 

800hp in the vette? What times will it run?