Originally Posted by heather lawn sp
2 997's 2500 hours, 72 inch & 60 inch
Kubota GF 1800 500 hours
John Deere 757 800 hours, 60 inch
John Deere F725 2nd engine (chassis 2500 hours)
John Deere M655 2nd engine (chassis 2100 hours), 54 inch
Diesel consumption 189 litres (50 US gallons) a week
Gasoline consumption 200 litres (53 US gallons) a week
The 9's pull about 400 hours a year the 757 & 655 pull about 250 per year.
The little 18hp Kubota will keep up with the re-engined 25hp L/C Kawi F725, both 54"
400/250 is 1.6. So if I read that correctly, your 3 diesels are running 60% more hours total, but burning 6% less gallons of fuel than your 3 gas mowers? That comes to almost exactly 41% less fuel burned.
I assumed the diesel and gas mowers were the same size and mow at the same speed. It's more than a 41% savings if the diesels cut more per hour.
Using $3.50/gallon to be conservative, and 50 gallons/week on gasoline, that's $175/week on gasoline versus $105/week on diesel. Buying ag diesel might make the savings a bit more, say $75, but even so, if you only save $25 a week on a mower running 400 hours a year, it will take a while for a diesel to pay for itself.
For a better analysis, I'd need the hours per week per mower.
Then I can plug in the numbers to show how much you save per hour on fuel. Again, I am assuming your diesels and the gas mowers cut the same area per hour.