Diesel vs. Gas engines on ZTRs

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

  1. gbparn

    gbparn LawnSite Member
    from TS, TN
    Messages: 7

    I am looking to buy a new mower and leaning toward a diesel (Ferris IS2500). But a small engine guy told me that he preferred a big gas engine to diesel engine because of torque. He said it was his experience that a gas engine could maintain blade speed better in thicker grass and he attributed that to the amount of torque the engine could produce. I had always understood that a diesel motor produced more torque over a gas engine, but he went on to say that was true only when you got into the higher horse powers (65hp and higher).

    The other issue with a gas engine I wonder about is ethanol. The higher ethanol blends (E15, E20 etc..) are coming in the not to distant future and conventional gasoline will be harder and harder to find. I have been hearing the service guys (and recently EPA) telling me how hard ethanol blended fuel is on small engines. I don;t want to buy a machine that wont have an easily available and compatible fuel supply in 5 or 6 years.

    Take costs out of the discussion and what are the advantages or disadvantages of either engine type.
    Is there a cut difference?
    Does a diesel "pull" better and keep on cutting on hills or rough terrain better than a gas engine or vice versa.
    Does anyone know how the engine manufacturers are planning on dealing with the ethanol levels? Will fuel injection engines help resolve the problems ethanol causes in small engines?
  2. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Messages: 17,828

    I can't answer the ethanol question for you, but I can speak to the deisel vs. gas issue a little.

    I have owned a few deisel compact utility tractors in the 21-26 HP range, and one in the 40 HP range(4110,4115,4500 JD's. I still own the 4115), and all of them would/will out torque my comparable gas tractors equipped with identical mowers. (my 4110(21.6 HP) compared to my 445 (22HP) for one example). Not even close. The deisel wins by a noticable margin in thick or weedy grass.

    I have never run a deisel ZTR, but I seriously doubt that having a gas engine on a ZTR could somehow make the gas engine superior all of a sudden. My ZTR has a gas engine, but if I had the funds to buy whatever I felt like, I'd buy a deisel without question. They're more fuel efficient too.

    Both Deere and Kubota tout their deisels as the way to go for seriously heavy cutting.
  3. Curtis

    Curtis LawnSite Member
    Messages: 161

    I've always thought diesels were heavier, giving you a better chance to rut a residential yard in a rainy period. The diesels and fuel injected engines are looking more attractive with the price of gas these days .

    MOHUSTLER LawnSite Bronze Member
    Messages: 1,376

    I am a firm beliver in a gas engine. Diesels are more cost and more headache. On the plus for a diesel engine, they will run for thousands of hours. But so will a properly maintained gas engine.

    The only people still buying Diesel mowers are farmers with fuel barrels. Other then that go with a gas engine.
  5. vinny_a

    vinny_a LawnSite Member
    from PA
    Messages: 20

    I disagree with that, lots of people are buying diesel mowers who aren't just farmers with fuel barrels.

    My uncle who is the Highway Superintendent for a town up in MA just bought several diesel JD zero turns to maintain the township's sports fields because they last so long, and power through grass when its thick.

    Last year I worked for a golf course on grounds crew and we bought a new Ferris diesel Z-turn and got rid of our old Toro gas Z-turn for the same reasons. I no longer work there but I still talk with my old boss and he says that they cut the same areas with the Ferris in half the time they did with the Toro (same deck size just different engines)

    I used the Ferris briefly before I stopped working at the golf course last year to mow an area of 7"+ grass that we only cut every month or so (time saving purposes) and the difference was amazing. The Toro barely had enough power to move while cutting the grass but the Ferris just plowed right through it, didn't even slow down.
  6. fireman9

    fireman9 LawnSite Member
    Messages: 172

    I just bought a used Hustler diesel and sold my Scag Wildcat ! The hustler has a 60" cut and 27 hp Shibaura diesel the Scag had 30 hp Kohler and 61"...
    I was a little worried about cut issues with the XR7 deck because the Scag did cut nicely but it HASN'T BEEN an ISSUE. The XR7 cuts nice and at full speed too. I've cut massive amounts of grass that would have stalled the Kohler dead in its tracks even at a crawling ground speed with the diesel and it doesn't slow down... All things considered the diesel Kicks A$$ in the power & torque department. Plus I've mowed the first half of my route this past week and I've only used a half of a tank of diesel fuel as compared to emptying both the tanks on the Scag. I've mowed this route for the past two years with that gas eating pig and it's always sucked both tanks dry! I simply can't believe I have only used about half of one out of the two tanks of fuel on this machine. WOW! Looking forward to see how many hours both tanks can go for...

    P.S---- I also own a FERRIS IS3100 and love it for the ride, It has the 26 HP Kawa, I knew it would be a little underpowered in the thick stuff, but thats not what I bought it for...flying over rough soccer fields it's great!
  7. 32vld

    32vld LawnSite Gold Member
    Messages: 3,983

    Are you comparing apples to oranges?

    What was the HP of the old Toro?

    What is the HP of the new Ferris?
  8. vinny_a

    vinny_a LawnSite Member
    from PA
    Messages: 20

    The old Toro (only a few years old) had the 27hp Kohler in it if I remember correctly. The Ferris has the 33 hp CAT diesel in it, so 6 hp difference which is significant but the Toro wouldn't even come close to cutting it. The area was on a very gentle slope so you could only cut going downhill, you had to turn off the blades and go back up the hill to cut another path because the Toro just couldn't handle it. The Ferris on the other hand had plenty of power going back up the hill. For what we used it for the Toro was a joke.
  9. pugs

    pugs LawnSite Gold Member
    Messages: 3,025

    You are comparing a ~750cc gas engine to a 1500cc diesel.
  10. ClassicLawnCareInc

    ClassicLawnCareInc LawnSite Senior Member
    Messages: 745

    If cost isn't an issue as the 1st post said there is no reason to not buy the diesel what so ever. I have 7 mowers, 2 gas and 5 diesel and the diesel wins hands down in ever dept. It has more torque, cuts thicker grass better, gets better mpg and is smoother. The only posible downside would be the fact that the diesel engine weighs about 150 lbs more, and i know as some people have said " on a wet lawn that makes a difference" I disagree. If your cutting a wet lawn any zero turn is going to leave ruts. And the diesel isnt more headahce or maintenance. It goes longer between oil changes and never breaks down for me personally. I have 3 john Deere 997 diesels, 2 Hustler diesels and two Wright brand gas stand ons. My oldest diesel has 1300 hrs on it my oldest gas engine has 1300 hours on it and Ive spent a good amount of money on repairs for the gas engine, and none on the diesel.

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