Diesel vs Gasoline

[CampStewart]

Ah, playing the range card...

Modern ULSD has 17-19% more potential energy than pump Gasoline. And the diesel cycle is slightly more efficient at converting that potential. For most emissions-legal trucks, the delta is about 20%. In other words, with engines of similar capability you'll go 20% further on the same volume of fuel with diesel. If the average fuel tank size is 25 gallons, that's perhaps the difference between 500 miles on a tank of diesel versus 415 miles with gasoline. 180 lbs of diesel versus 165 lbs of gasoline. At equal weight, you'd be able to carry 2 more gallons of gasoline, good for only 30-35 additional miles. Of course, the average diesel engine and related added components (DEF tank, intercooler and plumbing, etc) weighs perhaps 175 lbs more than the gasoline engine option (some are WAY more than that -- Cummins 6.7L comes to mind). That's about 27 gallons of gasoline for the same weight.

All told, a diesel truck with 25 gallons of fuel weighs about the same as a gasoline truck with 55 gallons of fuel, give or take. A Cummins 6.7L might get 20 mpg where the same Ram with a 6.4L Hemi may only make 15 mpg.

Equal overall vehicle weight:
25 gals x 20 mpg Diesel = 500 miles of range.
55 gallons x 15 mpg Gasoline = 825 miles of range.

Of course, if a diesel gets 20% more range per gallon, but the gasoline truck can carry 220% more fuel for the same overall vehicle weight, gasoline wins.

Or, if you're looking at VOLUME rather than weight, you'd run 25 gallons of diesel but to achieve the same range you'd need to carry 20% more gasoline, or a total of 30 gallons of gasoline. A gallon is 231 cubic inches. So having to carry 5 additional gallons of gasoline would take up 1,155 cubic inches or 0.668 cubic feet. That's right, less than 1 ft x 1ft x 1 ft... although most people know what a 5 gallon spare gas can looks like.

Of course, the US national average price of regular unleaded gasoline is currently $2.41/gal where pump diesel is currently $2.91/gal (eia.gov 02/10/2020 data). So that 25 gallons of diesel will cost $72.75 and 25 gallons of gasoline will cost $60.25. At 20 mpg diesel, that's $0.15/ mile. At 15 mpg gasoline that's $0.16/ mile.

Weight? Gasoline wins when it comes to overall vehicle weight.
Cost? About equal, but gasoline wins (especially when considering the Cummins option alone is over $10K, and there's still higher maintenance costs, higher repair costs, and DEF to factor in)
VOLUME? Yep, to go the same distance you'd need to carry 20% more gasoline which takes up... not much space

So it depends on which metric is critical to your application, and even the trip planned. Pinning your need for a diesel vehicle on "range" seems really quite silly, but again your particular and specific need may somehow really require that range where carrying a spare 5 gallon can would either push you over your payload limit, or maybe you couldn't possibly find another spot to carry another cubic foot of gear, and what you do carry is more critical than range. Your metrics, your decisions.

Thank You

 

[gnel]

My 2.8L diesel ZR2 has about 390 miles off-road range, as measured in the Anza Borrego desert this last weekend. That was everything from 60mph+ wash blasts to fully-locked obstacle climbing in collapsed sections of canyon. My on-road range is 500+ miles. These numbers will likely change when I switch to 33s, and the advantage may diminish.

A gasser ZR2, Tacoma, JKU/JLU just doesn't have that kind of range. I don't need to bring fuel when other trucks have to bring fuel, meaning I have more payload, more room in my bed and a lower cG. That's the real reason why I chose diesel (also, the PO ate the cost without passing it on to me).

One real reason to dislike diesels: they are heavy. My truck is 200lbs heavier than a gasser, with the majority of that on the nose and contributing to pitch. The gas version of my truck is far more sprightly, and lands better after a jump or carrying too much speed off a ledge. Even with a winch, the gasser is lighter in the nose. Mine has both the diesel and a winch, and I've scraped my nose more than anywhere else.

Another real reason to dislike newer diesels sold in the US: Mexico still hasn't converted to ULSD. I'm sixty miles from the border and would have to run a 40gal aux tank to make Baja travel doable.

Even if I hadn't bought a slightly used truck, the cost of the diesel engine option and the cost of diesel were immaterial to the choice.

There are pluses and minuses to both. The last thing any community needs is pointless Balkanization.

Your mileage will change for sure with 33s. I went from stock 29s to 32s and now 33s with a permanent Alucab (550 lbs) and saw my numbers drop with each change. I am still getting 25ish highway so its all good. I did love the 30 mpg and 600 miles to an 80 litre tank I was getting with the little oem tires but god it looked lame and drug its bottom everywhere offroad. Oh and I did get a tune with an increase of 40 hp and 35 foot pounds more torque so that helped with the mpg.

 

[SOneThreeCoupe]

I'd like to regear to minimize the problems with upsizing tires, but unfortunately the correct ratio is not made.

Ah, playing the range card...

I mentioned range because range is important to some people. It was a comparison point, as was the weight of the vehicle. It's minor, but it's something I thought about. Anything that's a road block to doing something may prevent you from doing it. If I remove road blocks, then I'm more likely to spend time in the wilderness. That's what mattered to me.

 

[Dalko43]

Ah, playing the range card...

Modern ULSD has 17-19% more potential energy than pump Gasoline. And the diesel cycle is slightly more efficient at converting that potential. For most emissions-legal trucks, the delta is about 20%. In other words, with engines of similar capability you'll go 20% further on the same volume of fuel with diesel. If the average fuel tank size is 25 gallons, that's perhaps the difference between 500 miles on a tank of diesel versus 415 miles with gasoline. 180 lbs of diesel versus 165 lbs of gasoline. At equal weight, you'd be able to carry 2 more gallons of gasoline, good for only 30-35 additional miles. Of course, the average diesel engine and related added components (DEF tank, intercooler and plumbing, etc) weighs perhaps 175 lbs more than the gasoline engine option (some are WAY more than that -- Cummins 6.7L comes to mind). That's about 27 gallons of gasoline for the same weight.

All told, a diesel truck with 25 gallons of fuel weighs about the same as a gasoline truck with 55 gallons of fuel, give or take. A Cummins 6.7L might get 20 mpg where the same Ram with a 6.4L Hemi may only make 15 mpg.

Equal overall vehicle weight:
25 gals x 20 mpg Diesel = 500 miles of range.
55 gallons x 15 mpg Gasoline = 825 miles of range.

Of course, if a diesel gets 20% more range per gallon, but the gasoline truck can carry 220% more fuel for the same overall vehicle weight, gasoline wins.

You're playing very loose and fast with those numbers.

Where are you going to store that extra 30 gallons of gasoline? That's a lot of space and payload you're taking up there.

I think the range factor is an important one and an area where the diesel excels. For the same fuel capacity, a diesel engine (of comparable torque output to the gasoline alternative) will get you farther. There are plenty of areas in Canada and the western US where that range factor would come into play...that's why you see so many Jeepers and LC owners carrying around jerry cans strapped to their roofs or back bumpers.

Which brings up another important difference. Getting auxiliary fuel tanks for diesel is much easier. As well, it is much safer to store diesel in the normal areas (pickup bed, back bumper, behind the rear axle fuel tank) compared to gasoline. Gasoline combusts more readily and there are certainly safety issues with storing it in certain areas on the vehicle...though for some odd reason, most overlanders seem to ignore that issue all together.

My experience has been that modern gasoline engines can get their advertised mpg's in ideal driving conditions. The second you account for any additional factors (bigger tires, heavier payload, cold weather, undulating terrain, ect.), gasoline engines, including the modern turbo's, lose their mpg's very quickly. So talking about what a truck might get in stock form on the highway is one thing...what it gets in an overland scenario compared to a diesel version is quite different.

 

[Dalko43]

Both the 6.2 and the 7.3 are easily serviced/repaired.

The PSD typically requires cab-off.

That video also reminds me of all the non-serviceable hoses/connectors on these new motors.
My 6.2 has 'em as well. Not impressed at all about that....

That's a Ford issue, not a diesel issue.

Ford's have required cab removal for diesel work for a while now...I'm surprised that hasn't pissed off the current customer base.

 

[plumber mike]

That's a Ford issue, not a diesel issue.

Ford's have required cab removal for diesel work for a while now...I'm surprised that hasn't pissed off the current customer base.

Agree.
However, It was my understanding that cab removal speeds the process but is not an absolute requirement even for head removal. It’s possible but not easy. They certainly weren’t designed for service outside of a mechanics bay.

 

[IdaSHO]

Its more of a matter of engineering.

Id argue that Ford designed the trucks with the intent to pull the cab for big services.
Its not hard, and it massively increases the reliability of the repairs.
Also reduces the amount of strain and labor on the mechanic.

No, Cummins and Dirtymax trucks do not need cab removal for most services,
but I prefer to have the better truck of the big three, so I stick to Ford.

That means a gasser Superduty.

 

[IdaSHO]

That's a Ford issue, not a diesel issue.

Nowhere did I say it was a diesel specific issue.

Read it again.

 

[Dalko43]

Its more of a matter of engineering.

Id argue that Ford designed the trucks with the intent to pull the cab for big services.
Its not hard, and it massively increases the reliability of the repairs.
Also reduces the amount of strain and labor on the mechanic.

Not hard? Well you need a shop to do that...big constraint for DIY-minded owners. But then again Ford has reputation for not caring to much about the DIY owner.

 

[IdaSHO]

Like everyone else, they play the odds.

Like it or not, the percentage of owners that buy brand new diesel pickups are not the DIY type.
And they shouldn't be. A large chunk of cash for such a truck with a decent warranty, a truck owner should barely open the hood.
Dont like it? Buy something else... But there is good reason Ford pickups still hold such a marketshare....

Once again, just more reasons to go gasser.
Much more DIY service/repair friendly, regardless of MFG.

 

[plumber mike]

Like everyone else, they play the odds.

Like it or not, the percentage of owners that buy brand new diesel pickups are not the DIY type.
And they shouldn't be. A large chunk of cash for such a truck with a decent warranty, a truck owner should barely open the hood.
Dont like it? Buy something else... But there is good reason Ford pickups still hold such a marketshare....

Once again, just more reasons to go gasser.
Much more DIY service/repair friendly, regardless of MFG.

I’m hoping that new 7.3 gasser feels more like GM’s old 8.1. The simplicity of the gas engine has appeal until I drive one. Total pig. I wonder if they do that on purpose to sell the 10k motor upgrade.

An Ecoboost option on the 8 cylinders would go a long way towards making a gasoline engine do the work of a diesel.

 

[lucilius]

That's a Ford issue, not a diesel issue.

Ford's have required cab removal for diesel work for a while now...I'm surprised that hasn't pissed off the current customer base.

That is inaccurate. Ford diesels do not require cab removal for maintenance....it just makes things a lot easier i.e. less expensive and time consuming.

 

[85_Ranger4x4]

Which brings up another important difference. Getting auxiliary fuel tanks for diesel is much easier. As well, it is much safer to store diesel in the normal areas (pickup bed, back bumper, behind the rear axle fuel tank) compared to gasoline. Gasoline combusts more readily and there are certainly safety issues with storing it in certain areas on the vehicle...though for some odd reason, most overlanders seem to ignore that issue all together.

Dual tanks used to be pretty common from the factory for gassers. It was a factory option on my truck.

It is hard to find tanks because JY's just stab tanks to drain them but I would like to add a tank to mine.

That is inaccurate. Ford diesels do not require cab removal for maintenance....it just makes things a lot easier i.e. less expensive and time consuming.

Certain years do require cab removal to work on the engine, mainly the 6.4L. Before they started getting crusty you could just lift the cab off the frame like a bodylift height (not requiring messing hoses and electrical) to like pull the turbo but with age it is easier to go all the way now.

 

[BigSwede]

If range is what is important we are screwed. The industry and every guy posting here claims a lift and bigger rubber is a must do to get into the club. 40 years later I realize every inch of lift and every inch of bigger rubber equals 1mpg. I went from 33/10.50s to 32/7.50s on a stock suspension and went from a best 17mpg to 22mpg without trying. That gives me another 95miles between gas stations. If I drive 12K miles a year, that saves me 160 gallons of gas a year. OR a 3500 mile trip for free.

Sort of off track but if range is important, throw out the lift and the big tires. You'll get a much better, more controllable ride too.

Lift, in and of itself, doesn't impact mpg much. All it does is add a little aerodynamic drag underneath, with a barely noticeable impact on mpg. I speak from experience, as I lifted my FJC 2.5" without changing tire size.

Bigger tires are a whole 'nother story, which is why I didn't change tire size.

 

[Kaisen]

You're playing very loose and fast with those numbers.

No, not really. The numbers are the numbers. Feel free to make your case for how they're not accurate

Where are you going to store that extra 30 gallons of gasoline? That's a lot of space and payload you're taking up there.

If you go back and re-read, the extra 30 gallons referred to WEIGHT.... diesel drivetrains are heavier, diesel fuel is heavier per gallon. Adding 30 gallons of gasoline only brought the gasser up to weight parity with the diesel.

Yes, volume of fuel is another consideration. Of course you glossed over that with the extra 30 gallons on board (same weight for weight) you'd also have an additional **325 miles of range**

Don't need the range, and don't want to take up the volume?

25 gals x 20 mpg Diesel = 500 miles of range.
33 gallons x 15 mpg Gasoline = 500 miles of range.


Therefore, to have range parity, a gasoline vehicle would have to carry an additional 8 gallons. The gasser would still weigh a lot less than the diesel, as 33 gallons of gasoline weighs 218 lbs versus 25 gallons of diesel at 180 lbs... a 38 lb addition. The diesel engine option alone offsets this 38 lbs by a large amount. My guess is that most guys on this forum could lose 38 lbs... yet they don't, instead blaming what they carry