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  1. #1
    Gold Member eagle107's Avatar
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    John Deere and New Holland/Ford Tractors

    Default Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Guys,

    I am currently in the market for a new John Deere X700 series tractor with a 7-Iron mowing deck. I am only going to use this tractor for mowing the farm and nothing else, much like any residential owner who also might do some snowblowing. Now, I love a diesel engine for the torque, longevity and fuel efficiency, but I have been asking myself is it worth a $1,000 more for the X748 diesel model instead of the X728 gas model? Well, my gut says, "Yeah it is, go for it," but my brain tells me, "hold on a second, is that really true?" So I went online and read all sorts of debates about "Gas vs. Diesel" and "X728 vs. X748," however, none of the debates I read provided comparison charts or anything somewhat tangible I could sink my teeth into. So I came up with a comparison chart of my own.

    After discussing the X728 and X748 with my dealer, I found X748 will give me at least a $1,000 more when I trade it in and JD rates the diesel engine around 30% to 25% more efficient then the EFI gas engine. Now that I have more information to help me figure out if a diesel engine would be more cost effective than a gas engine, I need to know what my target breakeven/trade-in value would be in 10 years. At the moment, I am thinking that I would trade this tractor in after 10 years.

    Below are things I need to compare/look at:

    1. I burn about 55 gallons a year to cut the property around the house. How long would it take to breakeven with the fuel savings? I also wondered what the fuel saving would be if someone burned 70 to 300 gallons a year.
    2. I use on-road diesel which is 30 cents more than gas right now in Western NY. I also compared if diesel was $.20 and $.50 more than gas. In addition, I do not have a tax number to reduce the cost of purchasing off-road diesel, so I cannot
    get that cost benefit and did not figure that in.
    3. What is the "true" future value of a $1000 trade-in for the diesel model? I know that my $1000 today will not be worth as much in 10 years. So a $1000 trade-in value in 10 year will be worth about $600.00 in today's money.

    So I built a model, crunched the numbers and came up with the comparison chart that I attached. The definitions of the chart's column's are below:

    1. The first column shows the retail cost of the X728 and X748, both with a 7-Iron mowing deck, along with the 5 to 20 year interval.
    2. The second column shows the combined cost of the X728 tractor and the 55 gallons of gas to run the tractor at a fixed price of $4.00 for the next twenty years. I know this is not realistic, but I am really looking at if diesel continuously cost $0.20, $0.30, $0.50 more than gas.
    3. The third column shows the combined cost of the x748 tractor and the 55 gallons of diesel to run the tractor at a fixed price of "$4.20, $4.30 or $4.50" with a 30% fuel savings.
    4. The third column shows the combined cost of the x748 tractor and the 55 gallons of diesel to run the tractor at a fixed price of "$4.20, $4.30 or $4.50" with a 25% fuel savings.
    5. The fifth column shows the X748's 30% fuel saving compared the X728.
    6. The sixth column shows the X748's 25% fuel saving compared the X728.
    7. The seventh column shows the future worth of today's $1000 - if I purchased the X748 today and received a $1000 trade-in value for the X748 after 5, 10, 15 and 20 years.
    8. The eighth column shows the X748 future dollar trade-in value plus the 30% fuel savings.
    9. The ninth column shows the X748 future dollar trade-in value plus the 25% fuel savings.

    Based on the results, I see the following:

    1. Columns five and six show I will never save enough in fuel costs running the X748 over the X728 even if I use 100 gallons of fuel a year for the next 10 to 15 years.
    2. Columns eight and nine show the net value of what my $1000 trade-in and fuel saving would be worth after 5, 10, 15, 20 years. At 55 and 70 gallons a year, I actually would be losing more money with a trade-in that I invested with today's dollars.

    However, not all is bad! If you are a landscaper, contractor or commercial user, then the diesel starts to shine when using 200 gallons or more of fuel a year for the next 5, 10, 15 and 20 years. Also, there is no doubt the fuel saving would be considerably more if you can get off-road diesel for the same price or less than gas.

    At the end of all of this, I will choose the X728 over the X748 as the tractors are pretty much the same except for the engines. Also, for me the X728 is only an adjunct tractor to cut the small stuff while I already have a JD 4520 compact tractor to handle the big stuff. However, if you are a typical residential user cutting grass and snowblowing a few times a year, then you are better off with the X728's gas engine. Though, if you are a power user cutting fields, using the PTO and other attachments, or a commercial user, then the X748's diesel engine is still the best option for you. Hope this helps anyone trying to compare these two tractors or the "diesel vs gas" engine situation I was looking at.

    Note: Please be aware I could not account for everyone's situations/variables. This really pertains to my situation and hopefully a typical residential user's situation. Also, I used the retail price of the X728 and X748 w/ the 7-Iron mowing deck for the comparison. Mostly like you could get a 12% to 20+% discount on the tractors depending on the dealer, rebates and etc.
    Attached Files Attached Files
    Last edited by eagle107; 01-26-2013 at 07:30 PM.
    John Deere and New Holland/Ford Tractors and stuff

  2. #2
    Veteran Member bigtiller's Avatar
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    JD 2720

    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Here is another comparison that I made 11 years ago with a 445 and a 455, each with a 62" deck;

    Back the mower out of the shed, run the throttle up to 1200 RPM's drive over to the edge of the yard, pull up on the PTO knob. The gas engine will die and the diesel keeps running, it won't even lug down.
    HAVE FUN

    Life is easier when you plow around the stumps.


    2720

  3. #3
    Veteran Member Deere Dude's Avatar
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    John Deere 3720

    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    I went through the same thought process when I was deciding between my X740 and whatever the gas version was at the time. I went with the diesel because they sure have a lot of power and sound nice besides that. You have most of the variables all figured out pretty well.

    My neighbor has a 720, I believe it is, and he goes through twice the fuel that I burn. If it was just the fuel involved and the 60 hours a year used, I would think the gasser would be a better deal.,


    I have one gravity barrel of diesel to supply both tractors and that saves me a lot of messing around with fuel cans. Of course I am partial to diesel anyway with tractors and trucks that I own and have owned.

    Now that I think about it, if I was overly sensible, I would NOT have a 3720 or a 740. I would probably do with a small 300 garden tractor and rent something a couple times a year and I would be money ahead. But, what the heck..... sometimes if you like something, you just have to go for it.
    JD 3720 with R4s
    X740

    Eat breakfast like a king, lunch like a prince and dinner like a college kid with a maxed out charge card.

  4. #4
    Gold Member eagle107's Avatar
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    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Quote Originally Posted by bigtiller View Post
    Here is another comparison that I made 11 years ago with a 445 and a 455, each with a 62" deck;

    Back the mower out of the shed, run the throttle up to 1200 RPM's drive over to the edge of the yard, pull up on the PTO knob. The gas engine will die and the diesel keeps running, it won't even lug down.
    I think we are in agreement here, even though I would not even do that with my 4520 and Woods 7' mower. It is like using a 24 inch wrench compared to a 12 inch wrench. The diesel will always have more torque than the gas engine. The one variable I do not have is using the tractor on large or steep hills. I could see where the diesel's torque would help a lot there and burn less fuel. But for a relatively flat lawn, gas would work fine. I would think the Kawasaki FD750D EFI gas engine should have a pretty good amount of torque especially when running the higher-capacity/higher-flow 7-iron deck; the grass processing with the 7-iron deck will be much better than the standard yellow Xtra decks. By the way, the new 2013 X7xx models are suppose to have a different standard deck that will have a higher-capacity flow like the 7-iron deck, but 7-iron will still be the top deck to get and are still offered on the 2013 models.
    Last edited by eagle107; 01-26-2013 at 07:33 PM.
    John Deere and New Holland/Ford Tractors and stuff

  5. #5
    Platinum Member tomd999's Avatar
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    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Hiya,

    Here are some other factors to think about in favor of the Diesel

    1) No storage hassles. Pull it in, change the oil and put a battery tender on it, all set. No draining gasoline or stabil treating.

    2) No ethanol headaches. The EPA (Employment Prevention Agency) is set to raise the % of ethanol in road gas to 20%, this will cause more issues with small engines, not to mention the loss of power associated with the increased ethanol ratio.

    3) Torque. There is no comparison between a gas and Diesel here, the Diesel will power through the tough sections without loading down or stalling. (the 3 cylinders have the advantage over the v-twin as well)

    4) Sq feet per hour, again, the Diesel with the higher torque rating will maintain a higher tip speed on the blades and power through the tough sections and in the lighter sections you can run a higher ground speed while maintaining the high tip speed, both helping you mow more sq feet per hour.

    5) Fuel storage. Gasoline is far greater storage risk than Diesel. It's vapors are explosive, so it can never be stored in a garage attached to a dwelling, it's storage life is very short, even with stabilizer, compared to Diesel.

    6) Diesel tractors sound cool.

    My 6 cents for what it's worth,

    Tom
    Big and little Green tractors, Orange tractors and one awesome brown dog.

    "Congelo nos opus, quantum punitor ingravesco"

    "Behold, like the wild azz in the desert, go I forth to my work"

  6. #6
    Super Star Member murphy1244's Avatar
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    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Why not a zero turn?
    Murph

  7. #7
    Gold Member eagle107's Avatar
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    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Quote Originally Posted by murphy1244 View Post
    Why not a zero turn?
    Yeah, that is what I am getting rid of and replacing it with the X728. My mother along with other family members do not feel safe running the Scag Tiger Cat I have.
    John Deere and New Holland/Ford Tractors and stuff

  8. #8
    Gold Member eagle107's Avatar
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    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    Quote Originally Posted by tomd999 View Post
    Hiya,

    Here are some other factors to think about in favor of the Diesel

    1) No storage hassles. Pull it in, change the oil and put a battery tender on it, all set. No draining gasoline or stabil treating.

    2) No ethanol headaches. The EPA (Employment Prevention Agency) is set to raise the % of ethanol in road gas to 20%, this will cause more issues with small engines, not to mention the loss of power associated with the increased ethanol ratio.

    3) Torque. There is no comparison between a gas and Diesel here, the Diesel will power through the tough sections without loading down or stalling. (the 3 cylinders have the advantage over the v-twin as well)

    4) Sq feet per hour, again, the Diesel with the higher torque rating will maintain a higher tip speed on the blades and power through the tough sections and in the lighter sections you can run a higher ground speed while maintaining the high tip speed, both helping you mow more sq feet per hour.

    5) Fuel storage. Gasoline is far greater storage risk than Diesel. It's vapors are explosive, so it can never be stored in a garage attached to a dwelling, it's storage life is very short, even with stabilizer, compared to Diesel.

    6) Diesel tractors sound cool.

    My 6 cents for what it's worth,

    Tom
    I though the Senate stopped the EPA from raising the ethanol rate to 20%. I read that 20% ethanol would cause too much corrosion damage to the current gas engines.
    John Deere and New Holland/Ford Tractors and stuff

  9. #9
    Super Star Member
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    Deere 110tlb, 4520, x749, x758, L130

    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    eagle 107,
    I do the vast majority of my work with the x749, 4520 and 110tlb, all diesel and one fuel setup. I have one 2 1/2 gallon gas can with 2 cycle mix for the string trimmers, saws and blowers. Whether you go gas or diesel is a personal preference imo, the diesel has more power than I need for mowing but comes in handy for the ground engagement tasks I do.

    I recommend you go with which ever one you prefer the most, that is as good a reason as any.

  10. #10
    Silver Member Labrat's Avatar
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    JD 2210

    Default Re: Diesel vs. Gas - X700 Series Tractor's Mathematical Comparison

    I went with the diesel for the fuel economy. I was constantly stopping to re-fuel my garden tractor and i planned on keeping my tractor for many years and figured the diesel would go double or more hours before requiring an overhaul. The torque, rattle and diesel oder are added bonuses.

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