How could this be?

[Road_Phantom]

I usually get around 13 mpg when pulling my 33ft,11000lb loaded, fifth wheel. That, of course, is on flat ground doing 60 with no headwind. My truck is a 2018 Ram 2500, diesel with a 373 axle rating.
I recently bought a 26 ft. travel trailer, 5000lbs empty and here's my dilemma. I pulled it on mostly flat ground, no wind and maintained 60 mph and was only getting 11-12 mpg. What gives? I was thinking maybe frontal area, but the fifth wheel is two feet higher up front, so I'm not so sure that's the case. Some other coefficient mathematical formula is at play. The truck empty remains the same as far as mpg is concerned. Any thoughts?

[StirCrazy]

I had the opposit effect when I traded in my 7800 lb 30 foot trailer for a 15000lb 40 foot 5th wheel with my short box diesel. with the trailer there are two huge drag plains one behind the truck and one behind the fith wheel. I would get about 12mpg cdn towing that, when I got the 5th wheel because of how close the front sat to the back of the truck cab and the shape it almost eliminated the one low pressure zone and my milage went up to 15mpg (cdn) when I bought a new truck that is now a long box my milage decreased a bit to about 13.5 mpg. aerodynamics plays a huge role in fuel economy once you get over 40mph, and the faster you go the more differene it makes.

Steve

[ktmrfs]

Fisherman wrote:

ktmrfs wrote:

1320Fastback wrote:

Skibane wrote:
Winter and summer gas formulations are a thing...

Diesel #1 could cause a small dip in mpg because of the increase cetane.

well, #1 has a lower energy content/gallon, that's more the cause of lower mileage, not the cetane rating. And about now is when "winter blend" diesel starts showing up at the pump which is either #2 with additives to lower the cloud point, or #2 and #1 blend, or a combo. But in any case expect a drop in energy/gallon with winter blend= lower mpg.

I had to bite my tongue for a while, somebody from the left coast trying to tell us about diesel fuel, lol.

well since we spend quite a bit of time in the winter in Idaho, MT, and occasionally the dakota's I've had plenty of experience with diesels and gas vehicles down to some pretty fridgid temps, Occasionally near -40F/C. And having previously lived in Montana for 25 years, I do have some knowledge about winter and vehicles.

[Grit_dog]

Fisherman wrote:


I had to bite my tongue for a while, somebody from the left coast trying to tell us about diesel fuel, lol.

Wow, lol....
Pot calling the kettle black there, bud? Or did Ontario turn conservative since I last checked?

PS, is Angus anywhere near Letterkenny? Could you get me Katy's autograph?
Pitter Patter, let's get at er...

[aftermath]

I agree with the need to calculate your mileage over a long period of time. I also agree with the winter formula for gas, and I don't have a clue about diesel. I don't have a clue, not because I am a west coaster, I have no idea because I have never driven diesel pickups.
All that said, I do believe that aerodynamics plays a huge part in mileage. I towed a white box 21 ft trailer and got about 11-12 mpg. I traded for a 25 ft. Airstream that weighted 2000 pounds more and got the same mileage. Airstreams are one of the best when it comes to airflow around and behind their trailers.
The interesting observation came when, after owning this trailer for a few years, I added the bike rack to the back. Now, after a few more years with this setup, I am getting between 10 and 11 mpg. It doesn't matter if bikes are attached or not, the rack itself has impacted the turbulence at the back of the trailer.

[Fisherman]

ktmrfs wrote:

1320Fastback wrote:

Skibane wrote:
Winter and summer gas formulations are a thing...

Diesel #1 could cause a small dip in mpg because of the increase cetane.

well, #1 has a lower energy content/gallon, that's more the cause of lower mileage, not the cetane rating. And about now is when "winter blend" diesel starts showing up at the pump which is either #2 with additives to lower the cloud point, or #2 and #1 blend, or a combo. But in any case expect a drop in energy/gallon with winter blend= lower mpg.

I had to bite my tongue for a while, somebody from the left coast trying to tell us about diesel fuel, lol.

[ktmrfs]

1320Fastback wrote:

Skibane wrote:
Winter and summer gas formulations are a thing...

Diesel #1 could cause a small dip in mpg because of the increase cetane.

well, #1 has a lower energy content/gallon, that's more the cause of lower mileage, not the cetane rating. And about now is when "winter blend" diesel starts showing up at the pump which is either #2 with additives to lower the cloud point, or #2 and #1 blend, or a combo. But in any case expect a drop in energy/gallon with winter blend= lower mpg.

[dodge_guy]

kellem wrote:

dodge guy wrote:
If you just bought it, I’m guessing the outside temp is lower. Lower temps increase fuel mileage!

I believe it to be the opposite, better milage in warmer months. Imo

Yes, I just seen that. Somehow autocorrect changed it to increase, I guess I need to start proof reading. Cold weather does decrease fuel economy.

[JIMNLIN]

ktmrfs wrote:
You need a few more trips under your belt to see if it is related to what you are towing or just road/wind/temperature/fill conditions.

This. A single tank mpg can be high or low.
I use a several tank average when figuring my trucks fuel usage. A single tank can be high or low number.

[1320Fastback]

Skibane wrote:
Winter and summer gas formulations are a thing...

Diesel #1 could cause a small dip in mpg because of the increase cetane.

[Skibane]

Winter and summer gas formulations are a thing...

[kellem]

dodge guy wrote:
If you just bought it, I’m guessing the outside temp is lower. Lower temps increase fuel mileage!

I believe it to be the opposite, better milage in warmer months. Imo

[Grit_dog]

Not that it matters, but FWIW, unless you re-geared your truck, it has 3.42 gears. Only final drive ratio offered on srw Ram diesels from 2014-2018.

[TurnThePage]

Last summer I took a couple kayaks on a camping trip for the first time. They were mounted on top of the truck cap. My mileage improved almost 2mpg. The cap itself affects mileage negligibly.

[Road_Phantom]

I'm going with the air flow effect. A cap might solve some of the mpg issues, which is in the future plan. Temps were in the low 80's day time to 60 at night for West Texas and the first drive from the dealer was around eight hundred miles. 11+ was consistent for all refills.