Diesel VS. Gas Which would you suggest

[Jason Mills]

I Picked up a M-37 to use as a plow truck on my driveway. Originally I was going to put a diesel engine in it, but with the price of diesel these days, and the fact that it needs to be plugged in for an hour before use has me wondering if a slant six in the truck would be as good or even a better idea.

What do you all think?

[MoparFreak69]

Gas vs Diesel, an often pondered debate by many.

To justify the expense of a diesel you have to consider how you use your truck. A diesel engine likes to be started at the beginning of the day and shut down at the end of it. Short trips to the grocery store or just down the street is very bad for a diesel engine, simply because it does not have enough time to warm up thoroughly and burn the carbon out of the combustion chambers/cylinders.
Semi tractor trailer rigs that run millions of miles generally never have to deal with cleaning injectors or carbon build up on parts because they run for many hours on end, vs Joe Homeowner that uses his truck for a 5 minute trip will wind up with lots of injector issues. GM found that out with the old V6 diesels they used to put in Buicks and such. Smaller TDI motors that VW/Audi run generally are a lot more tolerant because they warm up a lot faster than the bigger guys.

Another point; Yes, diesel is more expensive per gallon than gasoline. I used to run a Cummins powered Ram as my plow truck for my work. The company also ran 3 other rigs, all gasoline. Same sized tanks across all 4 rigs but I was refilling about once a week vs the gassers refilling almost daily. Why? Diesels are a lot more fuel efficient than a gas engine when being worked. The big key is to work it though. If you are plowing a driveway once a day, I would stick with a gas engine.

As far as cold weather starting, my Cumming Ram I mentioned above never had any issue starting in the coldest weather. I never plugged it into a wall outlet, mainly because the heating element was no good. Allowing the intake grid heater to complete a full cycle (usually took 20 seconds when stone cold) made it fire up on first compression stroke every time.

One last point; heat. How important to you is having cab heat quickly? My Ram took about 20 minutes of working before I could think about being warm. A gas rig will warm up and provide heat much faster than a diesel in pretty much any situation.

If you move a lot of weight and keep the rig running for hours on end, the diesel is the sure choice. If you occasionally move a lot of weight but generally use your rig in a grocery getter type of routine I would stick with a gasser to avoid the maintenance pitfalls the diesel will be sure to encounter.

[Desoto61]

There is something attractive about a diesel in these trucks. I couldn't resist it, but I agree with the above mostly.

The diesel setup will be more expensive unless you can find a good deal. A well used Cummins 4BT will tend to run 2-4 thousand, then you need all the pieces to make it work. You could probably look into a newly rebuilt gas engine for the same price. I figure I'll have probably 6K in the engine and trans setup for my truck unless I can find a good deal on the transmission.

You'll also need additional modifications to the fuel system (a return line has to be installed) and front suspension (add a few leaves to the front end for the extra weight, maybe a slight lift) that wouldn't be required for a gas engine in most cases.

But as said, the diesel will run forever if cared for, it can get great mileage and maintain it when worked hard, and they like to be worked hard.

[MoparNorm]

Gas vs Diesel, an often pondered debate by many.

To justify the expense of a diesel you have to consider how you use your truck. A diesel engine likes to be started at the beginning of the day and shut down at the end of it. Short trips to the grocery store or just down the street is very bad for a diesel engine, simply because it does not have enough time to warm up thoroughly and burn the carbon out of the combustion chambers/cylinders.
Semi tractor trailer rigs that run millions of miles generally never have to deal with cleaning injectors or carbon build up on parts because they run for many hours on end, vs Joe Homeowner that uses his truck for a 5 minute trip will wind up with lots of injector issues. GM found that out with the old V6 diesels they used to put in Buicks and such. Smaller TDI motors that VW/Audi run generally are a lot more tolerant because they warm up a lot faster than the bigger guys.

Another point; Yes, diesel is more expensive per gallon than gasoline. I used to run a Cummins powered Ram as my plow truck for my work. The company also ran 3 other rigs, all gasoline. Same sized tanks across all 4 rigs but I was refilling about once a week vs the gassers refilling almost daily. Why? Diesels are a lot more fuel efficient than a gas engine when being worked. The big key is to work it though. If you are plowing a driveway once a day, I would stick with a gas engine.

As far as cold weather starting, my Cumming Ram I mentioned above never had any issue starting in the coldest weather. I never plugged it into a wall outlet, mainly because the heating element was no good. Allowing the intake grid heater to complete a full cycle (usually took 20 seconds when stone cold) made it fire up on first compression stroke every time.

One last point; heat. How important to you is having cab heat quickly? My Ram took about 20 minutes of working before I could think about being warm. A gas rig will warm up and provide heat much faster than a diesel in pretty much any situation.

If you move a lot of weight and keep the rig running for hours on end, the diesel is the sure choice. If you occasionally move a lot of weight but generally use your rig in a grocery getter type of routine I would stick with a gasser to avoid the maintenance pitfalls the diesel will be sure to encounter.

Generally correct, however with new diesel technology and design and new oil tech, the start stop issues are no longer applicable on a modern diesel.
In fact two things to note, Cummins and Dodge are working on "Start-Stop" technology to conserve fuel and lower emissions and in most states it is now illegal to idle your diesel for longer than 5 minutes.

As for fuel prices, remember to run some simple math numbers when watching the price per gallon vs. cost per mile. Since diesels get approx. 30%-35% better fuel economy than a comparable gasoline engine, being used in the exact same manner, gasoline prices would have to be 30%- 35% Lower than diesel before the cost to operate was a push.

That means gasoline at $3.00 per gallon and diesel at $4.00 per gallon is the exact same cost to operate. Anytime the separation between diesel prices and gasoline is LESS than the fuel economy savings, then diesel is cheaper to operate.

Does the current gasoline engine work? If it works I would leave it alone for the simple reason that a $2,000 engine swap would take a long time to recover the diesel fuel savings.
If the truck has no operating engine, then diesel is the way to go, IF the cost to swap the engine is comparable between the Slant Six and the diesel (4BTA?)

IF all you are going to use the truck for is your own driveway, it would be cheaper to get a snow blower.
If you want the truck for other uses, then you have to do your own math to consider your anticipated use per year vs. the cost of the conversion or repair.

[MoparFreak69]

Generally correct, however with new diesel technology and design and new oil tech, the start stop issues are no longer applicable on a modern diesel.
In fact two things to note, Cummins and Dodge are working on "Start-Stop" technology to conserve fuel and lower emissions and in most states it is now illegal to idle your diesel for longer than 5 minutes.

While this is true you have to consider the original posters question/situation. He picked up an M37 to use as a plow truck. Probably got it just about dirt cheap and only wants to spend enough on it to get it pushing a plow. I doubt he will want to spend the $10K+ it would require to purchase the newer technology diesel engines, therefore relegating him to the 6bt/4bt generation, therefore applying all the information I provided above.
If you are out shopping for a brand new truck today your information has a lot of merit. Repowering an old truck for plow duty is about as far away from buying a brand new truck as you can get. He isnt going to care about emissions as something that old is exempt from any and all emissions standards. I could swap a black smoke belching diesel monster into my '59 W100 and never have a concern in the world as the '59 is exempt from all emission standards. I would never do this of course, but the loophole exists and people do take advantage of it.

[Charles Talbert]

Just a couple of things to add

We haven't done any repowers for grocery getter applications that I know of; so that can basically be tossed; don't think anyone has that intent.

MoparNorm has given the more common sense analysis thus far. The newer technology as with all electronic engines have brought new facts to the table; way better cranking and performance in cold weather, improved fuel economy as the electronic pump and injectors are soooooooooo much more precise than the mechanical stuff on the 4BT engines. I've been keeping up closely with current Cummins facts and the next round of big changes that will become the law in Jan 2014. Cummins is more on top of this new stuff coming than any others I've heard of. An example they have already perfected the technology to make the QSB4.5 engines we are installing now regulation compliant for after Jan 2014. No changes will be coming in the engine itself at all, but simply the addition of a single small component in the exhaust system. They have also perfected a way to run the engines at a higher coolant temp which will create a much cleaner fuel burn. There is a product already being marketed for some time now, Evans Coolant. This blend has no water, thus boiling at higher temps is not an issue. Running engines at higher temps is possible without the boiling factor in the mix, and it is done in a "0" pressure system. This coolant has been tested locally at engine temps up to a sustained 250*; no damage as this liquid is light years ahead of a water / anti-freeze mixture. It never wears out like anti-freeze thus it can remain in the system for vehicle life by following a few simple guidelines. Cummins has run this in engines with thermostats popping full open at 230*, off the charts better performance, cleanliness within the engine, and far less emmissions out the stack.

If you have practical, sensible application for your truck that would call for diesel; new technology is the way to fly for best all around economy and longivity. If you don't intend on an application where it would pay off; then another option is likely the better option.

[MoparNorm]

While this is true you have to consider the original posters question/situation. He picked up an M37 to use as a plow truck. Probably got it just about dirt cheap and only wants to spend enough on it to get it pushing a plow.

Yep, exactly WHY I also said:

Does the current gasoline engine work? If it works I would leave it alone for the simple reason that a $2,000 engine swap would take a long time to recover the diesel fuel savings.
If the truck has no operating engine, then diesel is the way to go, IF the cost to swap the engine is comparable between the Slant Six and the diesel (4BTA?)

IF all you are going to use the truck for is your own driveway, it would be cheaper to get a snow blower.

;)

[MoparNorm]

We haven't done any repowers for grocery getter applications that I know of; so that can basically be tossed; don't think anyone has that intent.

MoparNorm has given the more common sense analysis thus far. The newer technology as with all electronic engines have brought new facts to the table; way better cranking and performance in cold weather, improved fuel economy as the electronic pump and injectors are soooooooooo much more precise than the mechanical stuff on the 4BT engines. I've been keeping up closely with current Cummins facts and the next round of big changes that will become the law in Jan 2014. Cummins is more on top of this new stuff coming than any others I've heard of. An example they have already perfected the technology to make the QSB4.5 engines we are installing now regulation compliant for after Jan 2014. No changes will be coming in the engine itself at all, but simply the addition of a single small component in the exhaust system. They have also perfected a way to run the engines at a higher coolant temp which will create a much cleaner fuel burn. There is a product already being marketed for some time now, Evans Coolant. This blend has no water, thus boiling at higher temps is not an issue. Running engines at higher temps is possible without the boiling factor in the mix, and it is done in a "0" pressure system. This coolant has been tested locally at engine temps up to a sustained 250*; no damage as this liquid is light years ahead of a water / anti-freeze mixture. It never wears out like anti-freeze thus it can remain in the system for vehicle life by following a few simple guidelines. Cummins has run this in engines with thermostats popping full open at 230*, off the charts better performance, cleanliness within the engine, and far less emmissions out the stack.

If you have practical, sensible application for your truck that would call for diesel; new technology is the way to fly for best all around economy and longivity. If you don't intend on an application where it would pay off; then another option is likely the better option.

Thanks Charles! Good to hear from the Expert Diesel Man here!
I was hoping you would reply.

[Charles Talbert]

MoparFreak69, you might want to check a little further

Before swapping that smoke belcher into the '59 W100.

Now I understand you were just attempting to make a point with that statement; BUT, if you will go back and read the fine print that is among the literal pile of do's and don't's of the reg manual; I think you will find the regulation for older vehicles is not exactly like you said; and that any loop hole might be in the favor of the regulator's instead of in your favor. I'm sure this will probably vary somewhat from state to state; but basically the message that is conveyed is this; your '59 is pretty much exempt from the current regs as long as it has it's original engine or a replacement engine that is of the exact same specs as the original. Now once you go installing any other engine, be it gas, diesel, natural gas, propane fueled or whatever; you have now qualified your vehicle for the next chapter of regs. Your vehicle no longer falls under the exemption clause. They consider any major change such as a repower with any other than the original manufacturer's intended engine a whole other can of worms. You could have even used an older diesel that no longer meets current regulations, and common sense applied it may be light years better than the original as far as emissions go, but it still is not legal to install it in the eyes of the officials. True, in most cases nobody would likely ever pay it any attention; but if they did, good luck at proving legality to some federal or state flunky that is looking for a way to get into your bank account.

This is the very simple reason Cummins ceased to build as new the 4BT and 4BTA engines during the later part of 2008. New regs that were effective Jan 2009 disqualified the 4BT engines. They are still offered by Cummins currently as a ReCon engine. These are available for a limited time as replacement engines for vehicles that originally had 4BT engines installed as a new vehicle like I described above; it's days are numbered as far as Cummins is concerned. We purchased and installed our last 4BTA just before the end of 2008. We then retooled and started installing QSB4.5 engines that are currently regulation compliant and will continue to be compliant after the 2014 regulation change. The next major regulation change after Jan 2014 will be Jan 2019 unless the fed's decide different in the meantime; so the QSB series will be good to go thru the end of 2018 the way things stand right now. The engine you are running must have met current regulations that were in effect at the time it was installed into the vehicle to be 100% legal. This information was given to us by our Cummins Rep that calls on us biweekly. They look at all our diesel projects to be certain everything meets the approval of Cummins; both in the area of regulations and with the actual nuts and bolts of the installation.

I added the preceeding information to this thread just to convey some more current facts. In light of all this; if you are in an area where your vehicles must be certified and are subject to stingent vehicle and emissions testing as some states require. You may want to exercise care and do your homework before changing what is under the hood to something that is not compliant.

[MoparNorm]

Just to add to Charles' post. Last year, the Federal EPA adopted CA standards as the national standard. There are no longer CA regs and Federal regs, there is now one set of National EPA and CAFE regulations based upon CA.

CA has required that all diesels, even the ones previously exempt, must now undergo smog inspection, even though there were no requirements for diesel compliance at the time of manufacturer! Every previous exempt diesel, including mine, must be inspected prior to registration and license renewal.
It's an unprecedented disregard for the "grandfather clause" of nearly every prior regulation on the books and while it may never come to a state near you, it is possible and it sets a very poor precedent.

So, as always, buyer beware, do your homework and learn the regulations of your individual state prior to spending a penny and always use a reputable shop like Charles to perform first class work that counts.

[MoparFreak69]

We haven't done any repowers for grocery getter applications that I know of; so that can basically be tossed; don't think anyone has that intent.

MoparNorm has given the more common sense analysis thus far. The newer technology as with all electronic engines have brought new facts to the table; way better cranking and performance in cold weather, improved fuel economy as the electronic pump and injectors are soooooooooo much more precise than the mechanical stuff on the 4BT engines. I've been keeping up closely with current Cummins facts and the next round of big changes that will become the law in Jan 2014. Cummins is more on top of this new stuff coming than any others I've heard of. An example they have already perfected the technology to make the QSB4.5 engines we are installing now regulation compliant for after Jan 2014. No changes will be coming in the engine itself at all, but simply the addition of a single small component in the exhaust system. They have also perfected a way to run the engines at a higher coolant temp which will create a much cleaner fuel burn. There is a product already being marketed for some time now, Evans Coolant. This blend has no water, thus boiling at higher temps is not an issue. Running engines at higher temps is possible without the boiling factor in the mix, and it is done in a "0" pressure system. This coolant has been tested locally at engine temps up to a sustained 250*; no damage as this liquid is light years ahead of a water / anti-freeze mixture. It never wears out like anti-freeze thus it can remain in the system for vehicle life by following a few simple guidelines. Cummins has run this in engines with thermostats popping full open at 230*, off the charts better performance, cleanliness within the engine, and far less emmissions out the stack.

If you have practical, sensible application for your truck that would call for diesel; new technology is the way to fly for best all around economy and longivity. If you don't intend on an application where it would pay off; then another option is likely the better option.

Apples to Cumquats here.



I cant imagine that anybody is going to spend $20K+ (just for the motor) to repower an M37 for plow duty in their driveway, no matter how large it is (unless they are independently weathy and in that case they are not plowing their own driveway anyway).
Your information is relevant, just not in this case.
I dont think the original poster cares about transplanting an engine that meets Tier III and above emissions specifications. I certainly wouldnt spend that kind of money when a 4/6bt platform will fit just fine. Even at that, swapping in a 4/6bt requires only 2 wires to hook up after all the fitment/mounting that will be necessary with any repower. From my experience of swapping in an OBD-II MPFI 5.2 into my Wrangler (97 system=pre body computer and other CANBUS garbage) none of the new computer controlled are going to be even that simple to swap in. Too much work and engineering when their are better, and cheaper alternatives.
Black and white, any vehicle manufactured 1964 and earlier are not required to perform an emissions test in Ada county (where I live), Period. No mention of modifications, repowering anywhere because clauses like that do not exist. Why? Newer motors are generally known to produce less emissions so they dont care what you put them in.
Am I going to put a smoky diesel into my '59? No. I have no need for a diesel and will not waste the engine nor the money to put on in my rig. I am swapping in a Magnum 360 that will do all I need it to.
We are talking about repowering an M37 here, not a 2011 truck/car/van/whatever else(not that you would repower one of these rigs anyway).

Not tryin to seem like a jerk here, but while the information provided here may be nice to know for someone in the industry, it does not apply to anything on this website in any way. I basically take it as a "I know this about this so HA!" which really means nothing to me. Anybody can call a service representative and write down a bunch of information that means nothing to almost nobody. The information you provided means something to a company considering upgrading a fleet and wanting to maintain emissions compliances, or, well just about nobody else besides the manufacturer, whom happens to know a lot more about changes coming down the line way before they are ever published and known by the public. Case and point, working at the local Bobcat dealer I was often sent on week long training courses provided by Bobcat. They would tell us information like "Our latest engine line-up meets Tier III specs 2 years before they were required". What does that mean to anybody? Basically nothing unless a company is looking to purchase the piece of equipment for a government contract that specifically spells out the need to meet the Tier III requirements.
What does this mean to the original poster? Not a darn thing. He wants to know; repower with a diesel or overhaul existing powerplant. I gave my thoughts on the subject, the very basic, necessary information that would apply to the OP. I gave the information so he could make an educated decision that best fits hit situation. Tossing a bunch of facts and information around about what the industry is doing in 2013 does not fit this thread. By going off of your statement if you are considering repowering a Pinto you should go out and buy the absolute newest engine available so you can meet an emission requirement that will not apply to your vehicle. How much sense does that make? Who is going to put a Common Rail 6.7 into an M37? On top of that who is going to install a diesel exhaust fluid system in order to keep the emissions certifications for the brand new engine IN AN M37??? 230 degree thermostat? Really? How does that help here? 250 degree coolant at 0Psi? Useful information here or banter?

It seems like this is a case of "mines bigger" or "I know more about it than you do". Well, i'm not up for that game so I will bow out and let you enjoy your crown.

I hope the information I provided earlier is found useful to the original poster in making the decision of what route he wants to pursue with his M37 plow project.

Oh and a bit more info the OP might find useful. Diesel engines tend to weight a whole lot more than the original power plant the M37 came with. What this means is you have a lot more downward force being placed on the frame and suspension. Diesels also put out a boatload more power than the original power plant. This means more twisting forces are being placed on the frame and the rest of the drivetrain will need to be upgrade to handle the extra power. Consider the reinforcement that will be necessary as part of your work/cost of performing the swap.

[MoparNorm]

Reminds me of the adage, if you are in a hole and don't want to be, ...stop digging... = )
As I originally posted (and we have yet to hear a reply from the person that matters, which is the original poster):

it would be cheaper to get a snow blower.

[Jason Mills]

Reminds me of the adage, if you are in a hole and don't want to be, ...stop digging... = )
As I originally posted (and we have yet to hear a reply from the person that matters, which is the original poster):

I am appreciating everyone's perspective, and learning at the same time. I have been away since I posted the original question and will need to spend a bit more time digesting what has been said.

Wile it is true that a snow blower would be cheaper, I find they are slow as I am currently using a 84" one on the back of the tractor.. it works, and it takes a solid 60-90 minutes, from start up to finish.. great for 18" of snow, as you only move it once, not so great when there is 3 snowstorms of 6 inches each. (so I put chains on the car and ignore it till the weekend)

The truck is to be a work truck. snow plowing and hauling fire wood will be more likely than being used as a grocery getter. That being said, it is not a truck that will be towing a trailer 80% of it's time..

I am aware that diesel engines are better at 'work' then play.

The truck is engine less.. so I have total freedom.

[Jason Mills]

Gas vs Diesel,
Another point; Yes, diesel is more expensive per gallon than gasoline. I used to run a Cummins powered Ram as my plow truck for my work. The company also ran 3 other rigs, all gasoline. Same sized tanks across all 4 rigs but I was refilling about once a week vs the gassers refilling almost daily. Why? Diesels are a lot more fuel efficient than a gas engine when being worked. The big key is to work it though. If you are plowing a driveway once a day, I would stick with a gas engine.
.

This is a good point. How much of a "load" is the slant 6 going to be working under as it pulls the M-37 down the road- if it is working at 80% capacity then it will be little of an improvement over the flathead in terms of fuel "economy"

also comes the question, as to how well it performs the work being done. wide open in low gear would be a real drag (maybe that is an exaggeration) to have done all the work, and end up with it being way underpowered..

[MoparNorm]

Wile it is true that a snow blower would be cheaper,

More of a joke than anything, to make a point about costs, however since you answered the main question (the truck is engine-less now)

A few things to consider, fuel economy does not seem to be an issue for you, but power is.
That on it's face would eliminate 6 cylinder gas motor, unless you could find the original type engine and eliminate the cost of fabricating new mounts, trans adapter/trans etc.

The best running M37 I ever rode in was powered by a 360 V-8.
Food for thought.

PS, diesels aren't just for working, they are for great economy as well.
In a few years you will see an entire new generation of small powerful diesels in every type of vehicle.