InfoGraphic: Actual Fuel Economy of Diesel vs Gas Towing

[John&Vicki]

Being somewhat new at towing I haven't known how to feel about my 13mpg (gas) until reading this. Guess it's OK. Thanks for the info.

Poppy

[J. Morgan]

I would say 13 mpg gas is very good.

I am happy when I get better than 11.

[BoldAdventure]

I think we can all agree that diesel is just generally terrible.




<<runs and hides>>

j/k

[J. Morgan]

I think the execution of putting diesels in pickup trucks has been botched by two out of three manufacturers.

The unrealistic and nonsensical extreme EPA regulation of diesel engines has made things much worse.

There is a point of practical return that has been overtaken by regulation.

[TavnAsh]

My DPF and all the EPA crap kind of fell off my 08 cab chassis cummins right around 100,000 miles.. So weird that I now get about 3 mpg better empty/towing mileage (18-20/13-14).

The truck weighs 9200 empty and over 17,000 gross with the airstream.... We can accelerate up steep grades, have an exhaust brake, 50 gal of diesel (less flammable then gas), never worry about overloading and on average I run these trucks to over 300,000 problem free miles and sell them for over 1/3 their original purchase cost.ATTACH]217762[/ATTACH]

[perryg114]

I think our EPA restrictions are worse than those in Europe.

Perry

Originally Posted by J. Morgan

I think the execution of putting diesels in pickup trucks has been botched by two out of three manufacturers.

The unrealistic and nonsensical extreme EPA regulation of diesel engines has made things much worse.

There is a point of practical return that has been overtaken by regulation.

[dznf0g]

Originally Posted by TavnAsh

My DPF and all the EPA crap kind of fell off my 08 cab chassis cummins right around 100,000 miles.. So weird that I now get about 3 mpg better empty/towing mileage (18-20/13-14).

The truck weighs 9200 empty and over 17,000 gross with the airstream.... We can accelerate up steep grades, have an exhaust brake, 50 gal of diesel (less flammable then gas), never worry about overloading and on average I run these trucks to over 300,000 problem free miles and sell them for over 1/3 their original purchase cost.ATTACH]217762[/ATTACH]

Not weird at all. DPF regen sucks a lot of fuel and occurs about every 50 - 60 gallons of fuel burned. Although I find it to be about 1 - 1.5 mpg by studying the dash readout over a period of time and several Dmax trucks.

[TavnAsh]

Originally Posted by dznf0g

Not weird at all. DPF regen sucks a lot of fuel and occurs about every 50 - 60 gallons of fuel burned. Although I find it to be about 1 - 1.5 mpg by studying the dash readout over a period of time and several Dmax trucks.

The erg (exhaust gas recirculation) also came off, which when gone, allows cleaner, cooler denser air into the combustion process... That helped in addition to the dpf coming off. Added benefit is cleaner oil .


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[John&Vicki]

As many others have done, I've experimented quite a bit trying to see if there is a sweet spot where I get the best gas mileage. There are a lot of variables of course, but I imagine things start to smooth out as the sample sizes grow. I use cruise control almost exclusively while towing so thst may help keep things consistent.

I've experimented with 55, 58, 60, 62, 64 and 66 mph. My engine's (2007 MB ML500 V8) sweet spot seems to be 60-62, consistently better than the lower speeds.

I'm sure big haulers have developed computer chips that deliver optimum fuel economy for various conditions, such as temperatures, altitudes, fuel quality and grade, etc. i know it's common to swap chips in Porsches based on different performance parameters. Maybe it could be done in consumer TVs.

Poppy

[dznf0g]

Poppy, find a torque curve for your vehicle. Look for the RPM at which the curve flattens out and see where you are, RPM wise at given speeds in various gears.

With GM gassers and a 3.73 gear, I almost always find that spot at about 63 mph in direct drive. This was with 4 speeds. I haven't done an analysis in my demos with more forward gears.

That spot and right around it is most efficient under a heavy load on flat ground.

[TavnAsh]

Originally Posted by dznf0g

Poppy, find a torque curve for your vehicle. Look for the RPM at which the curve flattens out and see where you are, RPM wise at given speeds in various gears.

With GM gassers and a 3.73 gear, I almost always find that spot at about 63 mph in direct drive. This was with 4 speeds. I haven't done an analysis in my demos with more forward gears.

That spot and right around it is most efficient under a heavy load on flat ground.

That is another great thing about diesel trucks, big flat torque curves. My cummins makes it's max torque just over 1400 RPM and it stays at its max torque until around 2600 RPM, maxing torque at a lower RPM aids in efficiency and engine durability as the engine is not turning as fast as a comparable gas would be, gas engine's torque curves peak at higher RPMs. Also above 50 MPH, the biggest detractor from efficiency is drag from air flow (I am a professional pilot so I can get nerdy about this stuff). A car running at 70 mph is about 20% less efficient then at 50 MPH. Below 50 mph the largest detractor from efficiency is tire pressure.

So when I put that all in, the most efficient speed for us to pull the airstream is my compromise of 65 mph. There we are turning about 1900 rpm, and if all the tires are inflated properly, we get about 14 mpg on flat dry pavement on a no wind day. We can get better mpg going slower, but unfortunately our time is limited for vacations... The things I think about when I am the only one awake in the car ...

[J. Morgan]

At 65 pulling my 31 footer I will get about 10 Mpg, this adjusted for the higher price of diesel is going to be equivalent to better than 11mpg.

So dollar for dollar I give up about 3 mpg...

In 08 my truck cost me about 21k

Say I tow 20,000 miles a year, (I wish it were that much.) I will burn about 1800 gallons v. your 1400 gallons.

My additional cost per year at $4.00 a gallon is $1,600....

The Ram is a nice truck, the Cummins is a great engine, but it will take a long while to pay out, I say the Ford and chevy Diesels on average would never pay out.

[TavnAsh]

Originally Posted by J. Morgan

At 65 pulling my 31 footer I will get about 10 Mpg, this adjusted for the higher price of diesel is going to be equivalent to better than 11mpg.

So dollar for dollar I give up about 3 mpg...

In 08 my truck cost me about 21k

Say I tow 20,000 miles a year, (I wish it were that much.) I will burn about 1800 gallons v. your 1400 gallons.

My additional cost per year at $4.00 a gallon is $1,600....

The Ram is a nice truck, the Cummins is a great engine, but it will take a long while to pay out, I say the Ford and chevy Diesels on average would never pay out.

You make a very valid point. I honestly think at the recreational levels we use our trucks, it is difficult to justify a diesel by cost alone. I have other reasons, ultimately I think my diesel will be cheaper when resale and longer ownership intervals are worked in (I bought new for 33k in 08). But that also does not take into account what the extra $$ saved buying your truck could have done invested properly over the past 5 years... I probably would be a millionaire. Good discussion though, and I am working until 4 am, so it is keeping me awake!!! .


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[RVDreamer]

Originally Posted by J. Morgan

At 65 pulling my 31 footer I will get about 10 Mpg, this adjusted for the higher price of diesel is going to be equivalent to better than 11mpg.

So dollar for dollar I give up about 3 mpg...

In 08 my truck cost me about 21k

Say I tow 20,000 miles a year, (I wish it were that much.) I will burn about 1800 gallons v. your 1400 gallons.

My additional cost per year at $4.00 a gallon is $1,600....

The Ram is a nice truck, the Cummins is a great engine, but it will take a long while to pay out, I say the Ford and chevy Diesels on average would never pay out.

Wow, that Ram seems like a fuel hog!

My 2013 F-250 Diesel gets between 17 - 19 when empty and 13 - 15 when towing a 27 foot trailer. I usually do oil changes between every 5000 -7500 miles and that is the only time my DEF tank gets a refill.

I usually run 65 - 75 on the highway and have 40,000 miles on my current truck. I live in the Durango area so I am constantly changing altitude.

I have driven Ford Diesels since about 1988 and never had a lick of trouble with any model. My current Platinum F-250 Diesel Crew Cab is the best truck I have ever owned and I couldn't be happier.

Of course growing up in a farming family and later working in the oil fields, I always drove Fords due to durability and overall better work performance, so we are a bit biased.

[J. Morgan]

I Like Ford Trucks..... But my dads 6.0 power stroke is a POS period.

Great truck with a boat anchor engine.

The 7.3 diesels were good, all that has come out since doesn't impress me much.

[TavnAsh]

Originally Posted by RVDreamer

Wow, that Ram seems like a fuel hog!



My 2013 F-250 Diesel gets between 17 - 19 when empty and 13 - 15 when towing a 27 foot trailer. I usually do oil changes between every 5000 -7500 miles and that is the only time my DEF tank gets a refill.



I usually run 65 - 75 on the highway and have 40,000 miles on my current truck. I live in the Durango area so I am constantly changing altitude.



I have driven Ford Diesels since about 1988 and never had a lick of trouble with any model. My current Platinum F-250 Diesel Crew Cab is the best truck I have ever owned and I couldn't be happier.



Of course growing up in a farming family and later working in the oil fields, I always drove Fords due to durability and overall better work performance, so we are a bit biased.

I drove Fords until the 6.0 came out, then made the switch. I still miss my 99 7.3, awesome rig.

Trailer is a 30 bunkhouse around 8000 lbs and truck is a cab and chassis 4x4 with a steel tow bed, 9200 empty, 4.10 gears. We are running about 3-4k heavier then your setup. Empty 18-20 and with the airstream 13-14.


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[RVDreamer]

Originally Posted by TavnAsh

I drove Fords until the 6.0 came out, then made the switch. I still miss my 99 7.3, awesome rig.

Trailer is a 30 bunkhouse around 8000 lbs and truck is a cab and chassis 4x4 with a steel tow bed, 9200 empty, 4.10 gears. We are running about 3-4k heavier then your setup. Empty 18-20 and with the airstream 13-14.


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I also had a 99 7.3.

What amazed me with that truck was that I could run 70 keeping RPMs just under 2K and get 22 mpg or better under almost any circumstance.

Never had a truck do better for fuel mileage after that but my current truck is the quietest, cleanest, and nicest riding truck I have ever owned.

[rodsterinfl]

I think we can all agree that diesel is just generally terrible.

As a previous owner of a 2010 VW sportwagen TDI, I like the diesel but the reality of difference in initial cost, special oil/expensive filter changes, more expensive fuel costs-- made me rethink the whole idea of oil burner. Years ago my family had diesel rabbits and we loved them, all but the poorly designed add-on AC units with bad compressor brackets breaking from vibration (dealers had to add AC on them after the fact for the first so many years). Today though is a different time. The EPA has all but killed the benefit of diesels and if you look at the chart, right now the best engine would be the Honda or the Ford Ecoboost. I would not be able to use the wimpy Honda truck with my trailer weight so that leaves the Ecoboost.

There ARE applications that are better suited to diesel though as I said earlier no diesel UNLESS you need it. Bigger heavier trucks and fuel storage are the two benefits. Diesels are good engines and offer savings in particular applications.

[switz]

Due to some weight loss in the front of the truck, the turbo EGT reports 200 to 250 degree cooler running temperatures and does not exceed 1200 degrees in a hard uphill pull at 65mph with the GCVW at nearly 19,000 pounds. The cooling fan will occasionally come up to speed on a pull like this, but the engine is running at the recommended temps along with transmission and rear end.

Life is good.

[J. Morgan]

A point worth mentioning,,,, my combination weighs less than 12,000 lbs loaded and ready for camping.

Although some will say I am a liar, I have not encountered a hill on an interstate that I cant pull at 70 mph with my 5.3 gasser.

The slowest I have been is 42 mph on a somewhat long 8% grade south of Globe, AZ, I could hold this in second gear.