Question for engineers.

[chadm]

I was asked this question and do not know the answer.
i have a truck that driving at 80 mph using 1 gallon of fuel per 20 miles uses 4 gallons an hour.
A John Deere 730 tractor which can pull a 4 or 5 bottom plow shows at max it uses around 3 gallons an hour.

Why is current technology using more fuel per hour? Does driving down the interstate have more resistance then pulling the plow?

 

[CyCrazy]

Well the tractor is going probably 6-7 miles an hour at best. And I would have to think a truck driving 80 mph would have a lot of resistance to it. Probably also depends on diesel vs gasoline. I am not an engineer, but I can disc a field for 10 hours a day in a 1980's Case IH and not go through a full tank.

 

[DurangoCy]

Air resistance/Friction
https://phys.org/news/2015-07-properties-physics-affect-gas-mileage.html

This is one of the reasons that freight trains are so much more effcient than trucks, because they have little to no friction compared to trucks moving the same amout of good.

Let's build this hyperloop thingamabob.

 

[ropingcy]

There is also a big difference in horsepower, a JD730 would have just over 50 horsepower, your truck probably has 300-350 horsepower.

 

[Clonehomer]

I was asked this question and do not know the answer.
i have a truck that driving at 80 mph using 1 gallon of fuel per 20 miles uses 4 gallons an hour.
A John Deere 730 tractor which can pull a 4 or 5 bottom plow shows at max it uses around 3 gallons an hour.

Why is current technology using more fuel per hour? Does driving down the interstate have more resistance then pulling the plow?

Your JD 730 delivers a maximum of 53 hp. Your truck would use more than that to move its 2-3 tons at 80mph.

 

[jdcyclone19]

It comes down to horsepower, speed, gearing and engine displacement.

The higher the speed, the higher the load, the more fuel you will burn. The 730 goes maybe 3-4mph when pulling the plow, pulling a smaller load.

With your truck you are moving more of a “load” over a longer distance, per unit of fuel, compared to the 730.

 

[chadm]

Thanks for everyone's replies. Is it getting up to speed or keeping constant speed at 80 mph? . So the "load" on the truck at 80 mph is more then moving 7 feet wide of dirt 6 inches deep?

 

[NATEizKING]

Thanks for everyone's replies. Is it getting up to speed or keeping constant speed at 80 mph? . So the "load" on the truck at 80 mph is more then moving 7 feet wide of dirt 6 inches deep?

Most vehicles get their best gas mileage at 40-50mph and declines pretty rapidly after that so driving 80 is really burning.