Realilistic mileage with a fifthwheel.

Head and tail wind as well as speed is a very large factor. Remember friction increases exponentially or stated in physics by the square of the speed. Weight also plays a role but not as significant as speed and wind resistance. Weight comes in to play mostly when pulling up hill while gaining down hill. Driving habbits also plays a large factor with economy.
Saying that I generally get 12 mpg at 55-60mph with my Ford F350 SRW diesel pulling 39ft trailer for long distances that has a GVW of 16500. Not pulling I get 20 mph at 65-70mph. Also the quality of fuel plays a role while Ctane rateing is important. Most truck stops have a Ctane at a minimum of 40 except in states like California that require a Ctane of 50 which should provide better economy. Europe is mostly 50. Biodiesel does not have the BTU content of Diesel #2 and will not get the econmy as plain diesel. However, B5 does improve the ctane and is seems to be the sweet spot for mixing those fuels. My experience using B5 is mixed because one needs a controled environment to actually tell the difference. I don't use B20 if I can avoid it. I would never use pure jet fuel or biodesel because they burn much hotter and I question the effect on the turbo charger. Jet fuel simply does not have the additives that on-road low sulpher diesel has to lubricate the fuel system.

goducks10 wrote:
I get my best MPG while cruising on the net. Out in the real world it's lower for some reason.

Now =that's= funny! :B

Lyle

I get my best MPG while cruising on the net. Out in the real world it's lower for some reason.

10-12 miles per gallon sounds like a dream. I currently get right around 8-9, and that's on mostly flat grounds from Arizona to Texas.

-Phil

From a recent trip, based on gas station tickets and odometer:



Not saying that this is typical. I often do somewhat better. This is intended only as an example of documentation. I do not use the onboard computer. This is on a 2017 Chevrolet D/A 2500 with 34' trailer.

rhagfo wrote:

Earl E wrote:
Yep. 8-10 no matter what you are towing.

You must do all your towing at 70+, my 01 Ram gets 10 to 12 towing close to 12k. I would not expect much of a change going to a newer Ram.

Newer trucks have more pollution equip and will get worse than yours.

I agree with 8-10 mpg at 65 mph. Expect these figures in a late model diesel truck.

FWIW, since I'm running 265 tires instead of the OEM 245, my odo's off by 4%, which I recently rechecked over a 10 mile stretch of I-10. 10 miles by MP markers and only showed 9.6 miles, right at 4%. Every 100 miles I have to add 4 to get a "correct" mileage and it =does= make a difference. That said, my truck doesn't have the dash liar, but my 2 Hyundai cars do, and they're off anywhere from 1 to 2.5 mpg, in my experience. Only one instance on both cars have I had a hand-calc =less= than the dash and, maybe, 2-3 times each, where the mpg was < 0.5 mpg apart.

Lyle

I am NOT badmouthing anyone. I have towed West Coast since 05 first with a 5.9 12 valve at 20,500 combined at 60mph. My HAND calc average was 10.5. Next a 11 RAM 6.7 combined 28k hand calc 9.5 at 62. Current RAM 6.7 33k combined 9 at 60.

Tuners and tires will cause false readings.

I have an older 5.9 Cummins and your unloaded mileage figures are pretty realistic, only a little optimistic. But 12.4 mpg dragging a huge 5th wheel is just stretching it a bit. Perhaps your odometer is off a bit for some reason. Figure if you're averaging 12.4 mpg, sometimes you're getting 13 or 14 mpg. Only time I've ever seen over 13 mpg pulling my 15,000 lb. toyhauler was coming east into Amarillo with a 40 mph tail wind. It averages about 10-11 mpg.

Edited to show east into Amarillo, not west. East is pretty much all downhill.

fj12ryder wrote:

centerline wrote:
my '14 ram 3500 with 6.7 cummins, pulling the 5th wheel, fully loaded with 2 4wheelers and gear is 25,500lbs... at 60-65 we were getting an average of 12.4 traveling thru our western mountainous country...
BUT, 3 weeks ago I took the truck in for a recall on the catalytic converter, and now it gets 6-8 mpg.... WITH or WITHOUT the 5th wheel attached, regardless of speed.
they said to bring it back and they would fix it, as the upgrade shouldnt have made any mileage or power difference....

Sounds like they fixed the overhead readout so it's more accurate. :) 25,500 lb. 5th wheel and averaging 12.4 mpg...pretty unrealistic.

"pretty unrealistic".... you're thinking ford or chevy.

But I'll put my money where my mouth is... I buy my fuel at pacific pride. all the invoice's are kept on file as we have a business... what are you willing to put up to have me prove what I say?....

there are too many (jealous?) people who dont have a 6.7 cummins, but want to bad mouth them for some reason...
I have proof to back up my claim.

even after the recall upgrade, the dash readout is still fairly accurate, but I dont take my mpg avarage from the readout, as too many people have complained about the computer giving false information. I get it from the fuel invoices.

you dont have to believe, but the proof doesnt lie.

I had to edit, to make another "unrealistic" but true claim... without the 5th wheel connected, I got 22 to 24 mpg when driving 55mph.. and always 18-19 when running at 70mph...but not after the "upgrade"...