Fuel Consumption GPH

[Pete Judd]

Used HP vs fuel is very easy to figure out, and there are formulas out there, My little Yanmar, uses (under Load) about 1/3 of a gallon an hour, with the 5 ft brush hog, or the 5 ft finish mower. My 46 foot 16 ton sailboat with a 60 hp 4 cyl diesel, runs at about 1/3 per hour as well at 6 Kts speed. If I push up the speed to 7 Kts. At 7 Kts. will use .75 gallons per hour, and at 7.8 Kts, will be burning about 1.3 gallons per hour. The load is the key, not engine rpm. You can only get so much of a gallon of diesel.

But that said, some tractors are better than others, as gearbox, and engines can make a difference.

 

[pak7819]

Back in the day when I was still in the business the design criteria was 1/2 pound of fuel per horsepower hour. Kind of like outboard motors where fuel consumption in GPH at WOT = rated HP X 10%. Rule of thumb to get you into the ball park.

Opti-Mist: Is it coincidence that your reference to an outboard fuel consumption rate and your handle name (Opti,...max) might be related to a well known marine manufacturer in Fond du lac, WI?

Regarding "rule of thumb" design considerations, that is always at WOT under load, correct? Using 7 lbs for 1 gallon of deisel, 1/2 gallon = .071 lbs.

.071lbs x 40hp = 2.84 GPH,...if I'm using your "rule of thumb" correctly...

 

[jenkinsph]

Less confusing would be .5#'s x 40hp=20lbs/hour or 20/7=2.85 gph.

Off topic everytime I compare the Optimax to a more expensive Verado the Optimax seems to burn less fuel.

 

[Baby Grand]

285 hours 159 gal <> .56 gal/hr

 

[rd_macgregor]

There may be a confounding factor here. Is everybody using tractor clock elapsed time? I thought many (most?) tractor clocks actually recorded elapsed time corrected for rpm...essentially they are really recording total revolutions divided by some "standard" rev factor (usually in the neighborhood of 2500 rpm).
Or, have I misunderstood how this works?
BOB

 

[Jerry/MT]

The hour meters are correct at one rpm. But for the precision available for this discussion, I doubt that it makes a big difference. You'd have to measure the fuel with a high degree of accuracy and fill the tank to precisiely the same level each time and then adjust the time, know the lower heating value of the fuel, accesory loads, etc to get a high degree of accuracy and I doubt anybody in this discussion is doing that.

The numbers quoted here, at best , are probably within +/-5-10 % of the real answer but more likely ~+/-20%. So if you "measure " 0.5 gph, the truth is more likely somewhere betwee 0.4 and 0.6 gph. I worked in the aircraft industry and it cost us dearly to be able to measure fuel flow at better than 1% accuracy. (We actually calibrated our fuel meters with a large part of the actual fuel delivery system.)

Fuel usage is very dependent on load. To get a good idea of this look at the Nebraska Test data for any tractor. The BSFC (Brake Specific Fuel Consumption, lbs /hp-hr or sometimes gallons per hp-hr ) is generally presented graphically as a function of rpm at full load .(With the advent of the EPA ,"Full load" is usually determined by a visible absence of smoke now. In the old days it was a determined by a certain optical "smoke number".) It is also presented graphically as a function of load with rpm as a parameter. When you quote the fuel usage at rpm, fuel flow is all over the place because rpm does mean load.

As an example, an older Cat diesel has a BSFC of 0.61 @ 1000 rpm and 50 hp load and 0.45 @ 1000 rpm and 100 hp load (Ref: "Internal Combustion Engines" by Obert). So the fuel flow at 50 hp load is 24.4 lbs/hr versus 45 lbs/hr at 100 hp at a constant 1000 rpm.The fuel flow at constant rpm was over 1.8 greater for a doubling of the load in this example.

So unless you know the load it's hard to make meaningful comparisons of fuel usage.

 

[MHarryE]

Older tractors had hourmeters that read hours at X rpm, but every newer tractor I have seen has a digital electric meter connected through an oil pressure switch so it records hours when the switch is on and oil pressure is greater than a specific value, usually 5 psi or 0.3 bar.

 

[Jerry/MT]

Older tractors had hourmeters that read hours at X rpm, but every newer tractor I have seen has a digital electric meter connected through an oil pressure switch so it records hours when the switch is on and oil pressure is greater than a specific value, usually 5 psi or 0.3 bar.

Not "every new tractor". I have A 2007 New Holland and I have a mechanical tach/hourmeter.
And not "every" old tractor used mechanical clocks. I had a 1960 John Deere 435 and that used an hourmeter that used the oil pressure switch to start and stop the clock.

The point I was trying to make is that with all the other inaccuracies in determining fuel usage, the error due to the mechanical clock was insignificant for the purposes of this discussion.

 

[Chilly807]

Not "every new tractor". I have A 2007 New Holland and I have a mechanical tach/hourmeter.

My 2009 L3400 is the same, has a mechanical tach and hourmeter. It's surprisingly accurate, I was doing extended runs bush-hogging a field last summer at 540 PTO speed and tried checking the elapsed time against my watch.

I'd rather have the electronic one, to be honest. A lot of my running time is below 540 PTO speed. One solution for maintenance purposes is to change fluids more often, there's never any harm in that other than a minor dent in the wallet.

My "guess" at fuel consumption rates, and it IS a guess, is based on the number of hours I get before adding a fixed amount of fuel, usually pretty close to 5 gallons. Bush hogging, which is about 60% of full load under most of my conditions, yields a run time of about 5-7 hours before I add fuel.

Sean

 

[JDgreen227]

I started a thread in the "Fuels and oils" forum where I revealed my total fuel costs for both my vehicles and JD 4210 for the year. My calculations show my Yanmar 73 Cubic inch engine has consumed .623 gph for this year...about 85% of my operating hours are running a 60 inch MMM deck at 2300 rpm, 5% is snow removal, and the remaining 10% is brush clearing, rock moving, etc. Pretty happy with the overall economy, especially so because diesel rarely goes under $4 a gallon here.

 

[Chilly807]

Yeah, we're currently at almost $5 Cdn per US gallon here for diesel. It's more than gas here at this time of year.

Sean

 

[grsthegreat]

Yeah, we're currently at almost $5 Cdn per US gallon here for diesel. It's more than gas here at this time of year.

Sean

yeiks... its $3.80/gal taxed or $3.50/gal off road US here

 

[Baby Grand]

Just filled the yellow jugs at the corner for 4.30/gal here in CT, The Land of Steady Habits.
Unleaded Regular gasoline is 3.55/gal at the same place. Why diesel is so much more has me scratchin' my head. It used to be cheaper.

 

[JDgreen227]

Just filled the yellow jugs at the corner for 4.30/gal here in CT, The Land of Steady Habits.
Unleaded Regular gasoline is 3.55/gal at the same place. Why diesel is so much more has me scratchin' my head. It used to be cheaper.

Here regular gas is selling for $3.19 and diesel is always $4 or higher. I read somewhere else on another forum that when they refine a barrel of oil, they get more gallons of gas out of it than they would of diesel. Not sure if that's true or not.

 

[Chilly807]

I suspect it's due to the higher demand for heating oil at this time of year, in the summer months it's usually lower than gas.

Sean

 

[JDgreen227]

I suspect it's due to the higher demand for heating oil at this time of year, in the summer months it's usually lower than gas.

Sean

Not here, sorry to tell you...diesel is much higher than gas YEAR AROUND. The lowest I have seen diesel for the last few years is $3.75 and that was only for two or three days then it shot back up to $4.

 

[BethesdaEC]

Here regular gas is selling for $3.19 and diesel is always $4 or higher. I read somewhere else on another forum that when they refine a barrel of oil, they get more gallons of gas out of it than they would of diesel. Not sure if that's true or not.

Diesel has about 15% more energy per gallon which means 15% more raw oil. Gas requires more expensive refining than diesel, so back when crude was cheap, gas and diesel could sell for roughly the same and diesel was sometimes cheaper. Now that the raw material is more expensive it has moved the other way. Heating oil, diesel and jet fuel are very similar and the airlines actually purchase options on heating oil because there is no options market for jet fuel and they can covert the heat oil option into jet fuel very easily.

 

[Rara Avis]

You can find your Ag tractor test data here...
NE Tractor Test Publications

 

[schmism]

You're burning 0.5gal/hr, not 2/hr. Sounds about right - my L4200 use is similar.

JayC

My TC33 (33hp but hydro trans) on avg consumes .5 gal per hr. Ive recorded that over numerous tanks of avg use, both FEL work and lawn moweing with the MMM and also for the 40hrs we put on it digging a new drain feild useing the backhoe. (20 gal of fuel used, tracked and recorded)

Durring heavy work, heavy brush hoging, bottom plowing Ive seen that rise to 1gal per hr but im at high idle (2400rpm) and often hearing the engine pull down for extended times. (again tracked and recorded)

 

[slowzuki]

The amount you use per hour is completely dependant on what you're doing (how much hp the engine is developing)

My Kubota L5030 gets 12 hours or more out of its 10 gallon tank doing mixed loader stuff. It gets less than 4 hours of snowblowing deep snow continuously.

My MF5455 gets ? many days out of an almost 40 gallon tank on the wood splitter, it gets about 6-7 hours on the 10 ft discbine running wide open.