Diesel vs. Gas engines on ZTRs

Discussion in 'Lawn Mowing' started by gbparn, May 4, 2011.

  1. Mark Oomkes

    Mark Oomkes LawnSite Fanatic
    Posts: 12,164

    Interesting, we have very few problems with leaks. Or water pumps. Or hoses.

    Been using L\C mowers since '79 when we bought our first Toro Groundsmaster 72 with a 19 HP Continental. Sold that one with over 4,000 hours on it, had over 6,000 last I heard. The other 2 we had both had over 4,000 before our first major engine problem. Otherwise normal tuneups and oil changes. Never had a water pump on those.

    2 Toro 455D's, 1 Toro 4000D, a Howard Price 1260, Toro 3000-D, Exmark Lazer all had L\C since then. Coolant and leaks were never a major problem on any of them. Hard to say the cooling system was even a minor problem on any of them.
     
  2. hackitdown

    hackitdown LawnSite Silver Member
    Posts: 2,501

    Kawasaki L/Cs?
     
  3. Cummins343

    Cummins343 LawnSite Silver Member
    from Kansas
    Posts: 2,468

    All my mowers are kawasaki gas's with the highest one being 23hp. I also have a 72" Grasshopper ZTR with a 35hp Diesel. LOVE THAT MOWER! I've cut commercial accounts with it, accounts that would ultimately ruin a gas motor lol. I love that diesel. Doesn't burn as much fuel as a gas either imo.
     
  4. gbparn

    gbparn LawnSite Member
    from TS, TN
    Posts: 7

    Are there standard rpms the gas and diesel motor shafts turn? I understand the gas shaft turns at 3600 and the diesel turns at 2400. Some sort of industry standard for gas and diesels. If this isn't the case, I will keep looking for a mechanic.
     
  5. TLS

    TLS LawnSite Fanatic
    Posts: 7,940

    There are diesels that turn all different RPM's.

    ZTR wise, I've seen 3000 and I've seen 3800.
     
  6. heather lawn sp

    heather lawn sp LawnSite Senior Member
    Posts: 681

    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"
     
  7. TWerner

    TWerner LawnSite Member
    Posts: 80

    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.
     
  8. Mark Oomkes

    Mark Oomkes LawnSite Fanatic
    Posts: 12,164

    In what? :confused:
     
  9. hackitdown

    hackitdown LawnSite Silver Member
    Posts: 2,501

    Your lawn mowers.
     
  10. heather lawn sp

    heather lawn sp LawnSite Senior Member
    Posts: 681

    The argument for area isn't completely relavent, The big diesel mowers are open terrain mowers, the smaller gas mowers are hill climbing & close quarter trimmers.

    I'm working in litres here but the ratio's will be the same. Yes we are using marked diesel in the mowers.

    Gas $1.205, 2621 litres 2010
    marked diesel $0.9765

    Season for mowing is 25 weeks

    Excluding the small out front mowers as only auxilliary mowers, They will only burn a couple of gallons a week as back up's and specialty mowers, (steep hill work with 4x4, power sweeping, aerating).

    Each 9 goes out with a Z gas. unit 1 72" and 54". unit 2 60" and 60". The 9's of course are slightly faster. I've got the gas at 4.22 L/hr about 1.1 US gallon /hr.

    $5.06/hr 54 & 60 inch

    Still working up diesel numbers
     

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