InfoGraphic: Actual Fuel Economy of Diesel vs Gas Towing

[rp709]

The statement that diesel has a 113% energy content is about right. But energy efficiency has a lot to do with compression of the fuel air mixture. A Diesel engine extracts far more than 13% more energy from a gallon of fuel than a gasoline engine. Diesels are expensive because they can withstand far higher compression ratios. Therefore the diesel fuel cost is much lower than gasoline. In Ca diesel is about $3.10 and regular is 3.50 a gallon today, so it is even cheaper when measured by volume.
Gasoline powered airplanes use less fuel than jet powered airplanes. What would you rather fly? Towing with my Duramax is unlike the experience of any gas powered pickup.

[tjdonahoe]

From what I have gathered from people I know the duromax chev gets the better fuel mileage, I do like my 6.7 dodge towing the 31 classic the average is 12 mpg on a 4000 mile trip. There is no way I would go back to a gas powered pickup, as I like the power and torque especially at low rpm....

[Msmoto]

Just returned from nearly 3000 miles towing my Serenity. And, across the scales, 9260 lbs truck, 7140 lbs trailer. The truck has a full fuel load, about 90 gallons, plus the auxiliary tank weighs about 100 lbs. In the bed are generator, 160 lbs, tools, and other equipment, another 150 lbs. and the weight distribution hitch is dumping probably 600-800 lbs on it as well.

The trailer has two A/C units, Power Patio Awning, and had full water of 54 gallons.

So, with a GCVW of 16,400 lbs, I obtained about 12 mpg headed north west to South Dakota, into head/side winds of 20+ mph, then from Wisconsin back to North Carolina over 15 mpg, figured over 1000 + miles of towing. Speeds were 60 - 65 mph, more toward the 65. These figures are calculated from miles driven and gallons used, not from any on board computer. I record all fuel purchased in a log book.

My Dodge/Cummins has been tuned slightly by Pure Diesel in Kernersville, NC, and runs exceptionally smooth and powerful.

[slowmover]

MsMoto, are you maximizing the use of cruise control? There is at least a one mile mpg correlation between that and average mpg. For a Dodge, keeping revs at or below 2000 is big. I think your mpg are a bit low. As a test, is it a 30 or 40% reduction from solo? My rig is longer and heavier with a higher average at 63-mph as comparison. An 08 is emissions crippled, so delete of same with a mini max tuner is the usual "fix ". The percentage drop is the telling number.

Tjdonahoe, the day a MaxiPad gets better fuel economy on a model year and truck spec basis than a CTD is the day a lot of us will trade for one. A day that won't dawn.

[slowmover]

Re-read this thread. A lot of comments about the higher long term expense of owning a diesel pickup

Fuel is about half the long term cost. Depreciation plus other overhead is greater.

I bought mine because I knew the long term expense would be lower, and so it has been. 205k miles and have had to replace u-joints. Which might be called a wearing item, closer to a basic maintenance expense. Original clutch, one brake re-line, and recently installed second set of replacement tires. Etc.

Overall average mpg the past 55,000-miles is 21. 50/50 town & country.

As I'll keep it, it's time for me to start spending on it so as not to suffer breakdowns. Systematically, not piecemeal.

I did a close comparison some years back with another man who pulled our trailer type and also lived in the South Central US. Same truck, but with gasser motor.

What we found is that so long as diesel stayed under 50-cents higher than gasoline that fuel mileage was a wash.

But I doubt that his truck is still easily pulling a big trailer with a gas motor now with over 200,000 miles on it.

The curve favors diesel somewhere past 150k where other factors are the same. Pulling one our bigger trailers is no sweat to a Cummins, but a Hemi is getting a workout. Which I think adds to gasser longevity until the day it doesn't. Then it fades rapidly in performance.

Even more so a Cummins to choose as the diesel power plant since design life is far greater than the competition. Longest life and highest mpg.

To get back closer to what I perceived as the spirit of the thread, convert your towing and solo fuel cost to cents-per-mile. My towing cost fell ten cents per mile in the change from $4/gl diesel to $2.50/gl diesel. From 27-cpm to 17-cpm.

As the cost of an RV is divided into the annual nights aboard for value, the cost of the TV is between a commuter-mobile and the chosen tow vehicle spread. And it's not just FE, but all other associated overhead as well.

That's the economy. And has to be added into the nights aboard calculation. It's high. Why motels are cheaper, in general.

A diesel TV chosen for long term overall economy coupled to a TT that lasts a couple of decades without major work IS economy. For an RV. If the owner keeps the TT twenty years and only changes TVs every ten years or longer, then it meets the low cost parameter. For an RV.

[ROBERTSUNRUS]

Hi, Too many calculations for me; I just pay my bills and enjoy the trip. I don't know how long my vehicle will last and neither does anyone one else. Chances are I will never wear a vehicle out before buying another one. Cost per mile???? Who cares? I don't. My trips, my experiences, my followers, my pictures, my memories, and my stories are priceless.

[Msmoto]

My exhaust is unrestricted from turbo back. Tune is for max fuel mileage. Solo gives 20 - 21 mpg at 65 mph. I drive conservatively, use cruise almost all the time except in very hilly country better fuel economy comes with more constant throttle than constant speed.

I suspect the windy conditions may have played a big part in fuel mileage, and when not towing in South Dakota the 80 mph speed limit did not help economy....LOL


Ms Tommie Lauer
Greensboro, NC
2015 Serenity 30 RB / 2008 Dodge Cummins 4 X 4
WBCCI #4165 AIR #31871

[slowmover]

Yeah, those high rpm jaunts are like hitting a bad headwind. And if 21 solo, then 12.5 towing is a dead-on 40% penalty. Right on the predictive mark, so to speak.

[tjdonahoe]

I could probably limp down the road in the hills , like cooke city ,mt with a small gas engine pulling my 31 ' classic but I like the power and performace of the Diesel engine, it makes traveling easier.....

[rp709]

Jeff, excellent addition to my points. Throttled gasoline engines suffer significant pumping loss at anything less than wide open. This is another advantage diesel engines have. So, factor pumping loss, thermal efficiency with higher compression ratios and greater BTU content of diesel fuel and you see why diesel engines can see 50% better fuel mileage under load (towing).