When should we fill?

[Boondocker]

Do you have a feel for how much the extra diesel weight decreases your mileage?

[slowmover]

Probably isn't noticeable, Rodney. Most of us with diesel-engined trucks (well, at least with a Cummins under the hood) find that it is wind resistance, not the weight of the trailer or the bed load that is truly noticeable on most roads, with most loads, under most conditions.

A lot of start and stop, a lot of steep hills at slow speeds, all these would change the equation.

On my truck, with a 2,300-lb rated payload, an additional 800-lbs in the the bed [600# fuel/150# tank] is almost un-noticeable solo.

The truck would settle on the springs a touch, and I'd have to re-adjust the rearview mirrors somewhat. The "boulevard ride" would be improved a little. What would be noticeable would be braking into a corner too late, the body lean would be more pronounced; thus I'd be approaching more turns and corners even slower than my current slow style of driving.

The changed center of gravity is the real concern.

With a 1,000-lb tongue load from the trailer, a 300# bed topper, (a proposed additional 800# of tank/fuel) and a few hundred pounds of stuff, I would be near or at payload maximum. And I'd be more concerned about the axle maximum not being exceeded than the bed load. A Dodge, at least, is not undersprung/softly-sprung like the competition.

Once underway, on level roadway, the fuel mileage -- solo -- would be the same. I wouldn't expect it to change by much the towing mileage on most roads.

With the truck at maximum, and the desire to stay out of turbo boost pressure and keep low exhaust gas temps, I'd just be slower to accelerate, and sooner on the downshifts to slow.

Wind resistance is the measureable, noticeable change in fuel mileage.

[myboyburt]

Originally Posted by Gen Disarray

Do you have a feel for how much the extra diesel weight decreases your mileage?

Don't know as this truck is a TV only. That being said we are getting about 13 to 13.5 miles per gallon when we are towing our 25' Excella with a fairly full extended tank.

[SARGE/AF]

Originally Posted by Gen Disarray

Do you have a feel for how much the extra diesel weight decreases your mileage?

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXX
You had 1 person respond as far as Dodge is concerned, All your diesels are going to be basically the same, we don't notice the differences as far as weight because diesels are made and perform better under a load because of the higher tork they have. Generally a diesel will do better than a gas when loaded because they are in fact built for this. Where diesels usually suffer is when driven when not loaded and that is where gas really out does the diesel as far as fuel milage.

Sarge

[Bluto]

Gen Disarry,
I don't think there will be any negatives to fuel mileage because of weight, in fact, I believe that I will save fuel in the long run with less on and off hwy stops to get fuel while traveling.

[rwnash]

Just a few quick thoughts on the fuel economy vs weight issue.

By itself, extra weight increases fuel consumption because it increases tire rolling resistance. I worked in the automotive field before I retired four years ago and as a "rough" estimate we used to figure that each exra 1000 lbs of weight increased rolling resistance 8 to 10 pounds force. Diesel is about 6.5 lbs mass per gallon so an extra 50 gallons on average would weigh 325 pounds thus increasing rolling resistance about 3 punds force.

As has been correctly pointed out aerodynamic drag is the big factor here, and it increases with the square of the speed. While I never tested a truck and trailer combination, as I recall a typical half ton pickup had about 150 pounds force of road load (rolling resistance and aerodynamic drag) at 50 mph. Add a trailer and higher speeds and it will be much more - 250 pounds force? (It would be interesting to run a test but it would be expensive.)

Bottom line opinion: The extra fuel does hurt economy but the average trailer owner probably would not be able to detect it. I get about 15.5 mpg ( 2003 Chevy K2500 6.6 diesel automatic towing 6000 lb 25 foot AS) and 20 solo on the highway. An extra 300 lbs weight in the truck would reduce the towning mpg to 15.3 or 15.4 - less than tank to tank variability.

Hope this helps.

Whit Nash

[2airishuman]

good info whit.

while TOWING/TRAVELING the trailer the mpg issue will be very very small.

however IF using the truck for every day driving,

at home without the trailer and for lots of little stopngo trips...

hauling extra fuel (or 500 lbs of anything) isn't wise.

brakes will wear faster.

braking distances will increase.

trying to accelerate at lights, merging into traffic and so on will take more juice.

tires will wear faster, there is tranny wear, axle/bearing wear and so on....

for a truck that weighs 5-6,000 lbs carrying 5% or 10% extra mass in city driving is still real.

g.d.'s truck is NOT a big new diesel beast in the mold the new dodges, fords or that other company...

then there are the issues of NOT driving the truck (for weeks/months)

with 50-100 gallons of extra fuel just hanging around in the tanks...

cheers
2air'

[canadianguy]

Originally Posted by SARGE/AF

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXX
You had 1 person respond as far as Dodge is concerned, All your diesels are going to be basically the same, we don't notice the differences as far as weight because diesels are made and perform better under a load because of the higher tork they have. Generally a diesel will do better than a gas when loaded because they are in fact built for this. Where diesels usually suffer is when driven when not loaded and that is where gas really out does the diesel as far as fuel milage.

Sarge

Diesels are more fuel efficient than gasoline all through the power band. Not just under heavy load.

[rwnash]

2air,

Good Point. I was thinking of long trailer towing trips, not everyday use. Weight hurts fuel economy all the time and it will be worse in stop and go city driving. And, as you point out, it has other undesireable effects as well.

I am somewhat disappointed that AS trailers have gotten heavier over the years. The 75 TradeWind is about 4100 lbs while the similar 86 is about 1200 lbs more. We stopped by the local AS dealer 6 years ago, the 25 foot units were listed as over 6000 lbs! Over 40 years ago I remember lots of trailers being towed with passenger cars - granted they were more capable than todays cars. Still, for some of us that like to boondock off the grid, lighter trailers properly set up would be nice.

Whit Nash

[Airstreamer67]

I installed a 91-gallon RDS aluminum fuel tank recently. The tank is in the bed of my dedicated tow vehicle, a Ford diesel PowerStroke. This will cut my refueling stops by a factor of four.

I literally hate refueling my rig while on the road...looking for diesel pumps each and every day while traveling, competing with the truckers and/or autos trying to fuel-up in a 50-foot rig, and trying to figure-out whether a station even has diesel, where the diesel pump may be located, whether the credit card is suitable or if I have to run inside, etc etc etc.

The only time I ever damaged my Airstream was while trying to manuever in a tight filling station lot. I cut a corner too short while concentrating on finding the right pump to get to. This part of RVing really bothers me, and I'm too old for too much bothering. On a 3300-mile trip this Spring, I had to get soaking wet in a driving rainstorm running to-and-fro twice to pay for a load of diesel. I decided enough is enough. Hence, my new auxiliary fuel tank.

Since I also want to be able to use the tank to refuel other vehicles that I haul around on a utility trailer when not using the travel trailer, ie a tractor and RTV, I installed a fuel pump with a fuel filter and a regular fuel nozzle on the auxiliary tank. The pump is rated at 13 - 15 gallons per minute, so it literally takes about one minute of pumping time to fill one of my Ford's fuel tanks. For both tanks, it's two minutes. Of course, it takes just a few seconds to refuel the tractor and RTV.

I've found my setup works very well. In addition, it's a comfort to know that when a hurricane visits us again here in Louisiana, we have a lot of running time for either evacuation in the truck or for power generation during the long blackout time (the ole Boy Scout mode coming out again).

I have a fiberglass camper-top on my Ford. To access the filler cap for the auxiliary tank and/or the pump nozzle, I open a side window on the camper-top. The fuel hoses at filling stations easily reach inside, and the 10-foot hose on my auxiliary pump easily reaches my Ford's fuel tank outlets and those on the tractor and RTV.

Since my truck stays loaded with a lot of junk for RVing, and since I cover the fuel tank with a tarp, you would never know there's $500 worth of fuel sitting there. This is a comfort when thinking of all the crud looking around for liquid gold nowadays.

[Bluto]

I don't think anyone could argue about the convience of having an extra tank, but wait a couple of days, I'm sure there is someone out there that will say otherwise.
Your comments struck home with me as I feel the same way about stopping for diesel while traveling with a trailer in tow. Good luck and batten down the hatches, I see there is a storm in the Gulf now.

[slowmover]

Originally Posted by Dooley

Good luck and batten down the hatches, I see there is a storm in the Gulf now.

Here in CC we've been on the edge of the hurricane warning area for Dolly since Monday morning.

Since I don't yet have the extended range of an auxiliary or replacement tank, I was Monday mentally figuring the problem of towing from here to Laredo in evacuation traffic while on the way home from work:

With the 25-gallons I had onboard, the [estimated] 6-mpg of stop-and-go for the first 75-miles would take about half the total [useable] tankage. Even with the full 35-gallons on board, that is only 210 miles, maybe 170 before re-fueling. NOT enough for the entire Texas Gulf Coast evacuating (as happened with Hurricane Rita a month after Katrina).

An underbody replacement tank (60 or 75 gls.) is my preference, as I'd be using it constantly, my driving having gone up recently. The recommendation in the Gulf Coast is to keep fuel tanks above one-half, so, 31-gls at 6 mpg would be enough range to make Laredo and be out of the storm near a metro area (hopefully) not overrun with evacuees.

This truck is also very easy on brakes (at the miles in signature I am still on the first set of replacement pads), on the clutch and, well, as it is a truck, I expect it to have to work. The [I]acceleration[I] of wear is relative. The engine, unlike Ford or GM has an MTBO of 350m miles. I doubt I'll drive it that far. The clutch, front end & steering components, some suspension pieces, etc, will likely be replaced one time. With the aftermarket tank I'll have to keep to a tighter schedule of examining for wear -- maybe have to alter the front-end alignment -- but I doubt it will change much of anything that I am already doing.

The significant change will be in driving. Slower, with more room. (And I'll finally have the excuse for an exhaust brake to make it all easier). The other change will be to aftermarket, larger diameter anti-roll bars front, and a new one in the rear; with poly bushings (and, the best end links I can find). The truck already has BILSTEIN shock absorbers.

The one physical concern with a replacement tank is how it affects other components. The spare tire may have to hang down lower, and the planned Class V receiver (along with the anti-roll bar) will all have to be made to co-exist.