Why Diesel Engines are More Fuel Efficient than Gasoline Engines

[18CrewDually]

For me

but you would have more payload capacity out of the gasser vs the diesel…….

Both trucks are rated to 14k. 14k pounds is 14k pounds. Payload means nothing. Both engines are being asked to do the same amount of work on the same quantity of fuels.
Who wins?

 

[Tulecreeper]

Here's a test, and on topic for the thread.

My junk box 2018 diesel has a GVWR of 14k. Say I load it up to that 14k. Now take the same truck except it's a gas burning Hemi and load that upto the same 14k.
If we both left same place/time on the same path with a full tank of fuel of 32 gallons, who will go the farthest?

I already know the answer and I'm sure most of you do to.

You're talking a 3500. My comparison was for the 2500, and I wasn't talking about mileage. My comparison was between my RCLB with zero optional items against a standard diesel owner's truck that more than likely has multiple options and an extended cab, all of which reduce the CCC. If I had kept the same truck I have but just added the diesel, it would have raised my towing capacity by 4500# - which I would never use - but it would have lowered my CCC by 900#, which I will use. I bought my truck as an every day driver that also tows and hauls the most I could get out of it.

Everybody has their reasons for getting the truck they got. Mine was towing and hauling a decent amount of trailer and cargo. Besides, the diesels they have these days take too much care and feeding. I live rural and I picked up this truck in March and just went over 2800 miles. That's an average of 350 miles per month. Of those 2800 miles, there are maybe 500 of them at highway speed. All the rest is at 35 - 45 MPH. My kind of driving would kill a modern diesel engine.

 

[Units]

Both trucks are rated to 14k. 14k pounds is 14k pounds. Payload means nothing. Both engines are being asked to do the same amount of work on the same quantity of fuels.
Who wins?

That was an attempt at comedy. I drive a diesel, I get it.

 

[jejb]

Same old, same old. Do we all realize nobody in this thread has even asked the question of should they get a diesel or gasser?

Hope y'all are having a good Monday.

 

[Jimmy07]

Here's a test, and on topic for the thread.

My junk box 2018 diesel has a GVWR of 14k. Say I load it up to that 14k. Now take the same truck except it's a gas burning Hemi and load that upto the same 14k.
If we both left same place/time on the same path with a full tank of fuel of 32 gallons, who will go the farthest?

I already know the answer and I'm sure most of you do to.

The gasser, because the diesel will have to go back and get the other ~1000lbs of whatever load it is the two tucks are carrying to their final destination…

 

[Tulecreeper]

Both trucks are rated to 14k. 14k pounds is 14k pounds. Payload means nothing. Both engines are being asked to do the same amount of work on the same quantity of fuels.
Who wins?

Payload means everything. You will always run out of payload capacity before you run out of towing capacity.

 

[18CrewDually]

Well the thread was on diesel efficiency and nobody wants to answer my scenario. So much for trying to get it back on topic that diesels are more efficient.

 

[18CrewDually]

Payload means everything. You will always run out of payload capacity before you run out of towing capacity.

I'll try one more time with ya. And we can use 2500 this time.

Lets say Johnny has a 10k GVWR Hemi truck sitting on the scales and then loads it right upto 10k pounds by filling the bed with apples.
Sally also has an identical 2500 but her truck has the diesel. She does the same as Johnny and gets loaded to 10k pounds too.
Now they both leave the scalehouse on a full 32 gallons of fuel.
Who makes it the farthest before running out of fuel??

If you bring up payload again I'm done. Lol

 

[Curmudgeon]

DIESEL is 90 cents more

It varies, by brand, by location, and by gasoline grade.
My station right now, and being retired I use "Premium"
93 octane, driving about 6,000 miles/year.

Regular	Midgrade	Premium	Diesel
$3.74	$4.04	$4.44	$4.80

 

[Tulecreeper]

I'll try one more time with ya. And we can use 2500 this time.

Lets say Johnny has a 10k GVWR Hemi truck sitting on the scales and then loads it right upto 10k pounds by filling the bed with apples.
Sally also has an identical 2500 but her truck has the diesel. She does the same as Johnny and gets loaded to 10k pounds too.
Now they both leave the scalehouse on a full 32 gallons of fuel.
Who makes it the farthest before running out of fuel??

If you bring up payload again I'm done. Lol

I have no clue as I don't know what kind of mileage the 6.7 Cummins gets. I would be able to get about 400 miles...+/-.

 

[rzr6-4]

Payload means everything. You will always run out of payload capacity before you run out of towing capacity.

As I've said before, growing on the farm and pulling lots of sketchy s*** in my time, I know what it can handle. I really don't care what the sticker tells me my capacity is. My brother's diesel has a lower towing capacity than my gasser, but if we are taking a 20k gooseneck across the county we are using his without a doubt.

 

[Curmudgeon]

Well the thread was on diesel efficiency and nobody wants to answer my scenario. So much for trying to get it back on topic that diesels are more efficient.

Hey now, I thought I answered it, IMHO, in post #5.
Note, I don't own a diesel and never have, just looking
at the numbers, and listening to friends who have driven both.

 

[sealion]

I swapped my 1996 F150 straight six 300 for my current 2014 Big Horn 3500 6.7 Cummins Diesel. The F150 was getting around 15mpg, the Ram gets up to 25mpg! Incredible to me, I love it!

 

[olddog]

Diesel engines are more efficient for another reason that I didn't see mentioned in the OP link. Diesel engines do not have a throttle plate. A throttle plate means at light loads (such as cruise conditions) the gas engine is using power to run as a vacuum pump for the intake portion of the 4-stroke cycle.

Another observation; diesel engines waste less heat of combustion. That is why a diesel at idle doesn't warm up quickly. Also why a diesel is slower to heat the cabin in winter from a cold start, even while driving.

 

[Marshall]

Although I'm happy to be getting pretty much the same MPG with my '14 5.7 QC gasser as I was getting in my '06 QC 4.0 V6 Tacoma - city, highway, and combined, I have no intention of disagreeing with the OP or the link.

No hate here. But Diesel trucks can be pretty spendy and I got a deal I could afford on my Hemi.
Even considering I have never towed with my truck I'm still seeing reports of certain Diesels getting substantially better MPG under all conditions.

I have never had a small diesel in a pick up, but I have run 2 Massey combines, same model & size ,one had a Perkins diesel, other had a 327chev motor.
The Gas used 50 gal/ day, the diesel would make almost 2 days , running side by side.
Had a 78 heavy IHC truck with a 855 Cummins , That thing was great on fuel compared to my
gas 3 tons , the 3 tons weight about the same loaded as the heavy did empty.
But like comparing apples to oranges, here .
This was all before the silly stuff they hang on the motors these days

Brother has a 1 yr old Chev duramax, he tell me it gets about 15 or 16 empty or loaded.
He had one before that , same thing.
You load a hemi down , the numbers go down the tank. Running around like a car, it is great, with the 8 speed.

Starting a diesel at - 20 or -30 is a whole different ball game if you don't have a heated shop

 

[KKBB]

I have no clue as I don't know what kind of mileage the 6.7 Cummins gets. I would be able to get about 400 miles...+/-.

I can tell you...the Cummins wins. Hands down, every time!!

 

[Docwagon1776]

I'll try one more time with ya. And we can use 2500 this time.

Lets say Johnny has a 10k GVWR Hemi truck sitting on the scales and then loads it right upto 10k pounds by filling the bed with apples.
Sally also has an identical 2500 but her truck has the diesel. She does the same as Johnny and gets loaded to 10k pounds too.
Now they both leave the scalehouse on a full 32 gallons of fuel.
Who makes it the farthest before running out of fuel??

If you bring up payload again I'm done. Lol

Trick question. 10k lbs in the bed results in both Johnny and Sally being crushed to death in a tragic apple avalanche before either runs out of fuel.

 

[Mark Harrison]

Tell you what when you hookup a 6000lb trailer behind my cummins 5.9 and go over any highway pass at 70 mph you will enjoy the power and mph of the diesel .

 

[Chief98]

Hey now, I thought I answered it, IMHO, in post #5.
Note, I don't own a diesel and never have, just looking
at the numbers, and listening to friends who have driven both.

My 2021 1500 2WD Ecodiesel routinely does 32-33 MPG on the highway at 74MPH. Thats almost 50% better than the Hemi. Diesel cost is typically 20-40% more in cost. Incremental maintenance (45K miles in) is roughly $200-$300/year. The math for me is basically break even at 50% higher cost and very positive at 20% higher cost. I shop it and typicaly pay 20% more. That said, I get 700 miles range at fill up, and i love the way the diesel drives with the 8 speed transmission. Also, with 50% better gas milage i have less emmissions than gas. Stellatis seams to miss this point while cancelling the diesel and going EV. Looks like my next truck will be a GM product to get a diesel.

 

[RickyJ108]

I pull a 30' camper started with an 06 Dakota, then went to an 07 Ram 1500, both pulled it one scary, one nicely but no room to grow, I finally bought a 14 2500 Mega cab 6.4L. I did a lot of research the diesel would be great for pulling living in the northeast we may get out 15 times a year so I'd be using the diesel for 30 days out of 365 days a year. the cost of 2 fuel filters and an oil filter was over $300.00 without oil. Normal driving for me is 12 miles a day barely enough time for the diesel to warm up. Should we buy a bigger camper my 2500 will tow it. My opinion diesel power wins. But for my usage the 6.4l gas takes the rest of the game.