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> Mpg, gas vs deisel
t5vr
post Jan 9 2010, 12:36 PM
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What should I expect for MPG with gas and with diesel class A. I now have a GMC 3/4 ton 4x4
and pull a 37' 5th wheel. I get about 8 MPG when pulling. i am planing an upgrade to a class A
of new 5th wheel with a diesel PU. Any thoughts? Thanks
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abbygolden
post Jan 9 2010, 01:08 PM
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QUOTE(t5vr @ Jan 9 2010, 12:36 PM) *

What should I expect for MPG with gas and with diesel class A. I now have a GMC 3/4 ton 4x4
and pull a 37' 5th wheel. I get about 8 MPG when pulling. i am planing an upgrade to a class A
of new 5th wheel with a diesel PU. Any thoughts? Thanks


For a gasser of comparable size, don't expect to get much more than 7 - 7.5.

You're not (necessarily) upgrading, you're just changing the type of RV from what you presently have.
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abbygolden
post Jan 9 2010, 03:36 PM
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QUOTE(t5vr @ Jan 9 2010, 12:36 PM) *

What should I expect for MPG with gas and with diesel class A. I now have a GMC 3/4 ton 4x4
and pull a 37' 5th wheel. I get about 8 MPG when pulling. i am planing an upgrade to a class A
of new 5th wheel with a diesel PU. Any thoughts? Thanks


For some reason, the answer I submitted several hours ago isn't here, so I'll try again. Expect about 7 - 7.5 mpg on a gasser (some will say more, some less), diesel should be slightly better. As I told you in your other thread, you aren't necessarily upgrading from a fiver to a MH, you are simply changing classes of RV.
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John Blue
post Jan 9 2010, 08:24 PM
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This is a tough one to call as a large number of factors come into play here. Items like how fast do you drive, do you travel in mountains or flat roads, do you keep the correct air pressure in your tires, do you keep up the PM's like oil and lubes up? Everything can change the fuel mileage. At times you drive into head winds and other times a tail wind.

We have an 8.3 Cummins diesel engine and we get from 8.5 to 10 MPG on average. One trip coming out of CO we run 11.6 but it was a small grade down hill to the Mississippi River. Our mileage had been about the same year in and year out. We drive around 62 to 65 on interstate roads and 55 on all state and county roads.

The gas engines will run a little less on MPG as they need to work a little harder.


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John
Brandon, Fl.
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Foretravel MH
Honda CRV tow
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Robie
post Jan 14 2010, 12:22 PM
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There is a vast amount of information around on this subject from one end of the scale to the other. The fuel millage you would get with a diesel will vary with size of unit, total weight of unit when loaded, type of area you are driving through; climbing hills or flat land driving. Also how you drive is a big factor. I can only give you my experience with the Dodge diesel trucks I have used for over 20 years. The truck I use to tow my 38' 5th Wheel is a year 2000 Dodge 0ne Ton 2X2 extended cab with duel rear wheels. My current 5th Wheel is a 38' 2009 Montana with an empty weight of 15,555 LB. The loaded trip weight is somewhere around 16,200 LB. Traveling fuel mileage has been right around 11 to 12 miles per gallon on both the truck computer and calculating the old way, by filling the tank full, then at the next fuel stop take the fuel used and mileage driven to calculate the fuel miles per gallon. I have noted that if I am filling up with B5 or B20 biodiesel mix I get 1 or 2 miles per gallon less. If I fill up with regular #2 diesel the mills per gallon have been as high as 13 to 14 miles per gallon. Also your driving style has a great deal to do with the full economy you get overall. I use a tow speed of 60 to 65 miles MPH on Interstate and in six gear the engine RPM is keep below 2000 RPM. This brings me to the type of transmission you have in your truck. I like a manual rather then an auto. The manual will always get better mileage over the auto if driven right. I am old school with a manual trans and I am in the minority. This information is based on my personal experience with my truck and I am sure other Dodge owners my not agree and me and get less mileage with there truck. Remember driving style is a major factor in the fuel mileage you get when towing. I you like to tow the same way you drive without the trailer and have a big foot you will not get good fuel economy with any truck gas or diesel.


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RLM
post Jan 15 2010, 08:31 PM
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First to answer your question. I normally get 8-9 mpg in my 40 ft diesel pusher motor home towing a 3200 pound vehicle. It was 6-7 during a recent trip out west in mountainous terrain. Most people will not get optimum mpg unless they change their fuel filter more often than recommended and are diligent in maintaining RPM and torque vs speed values listed in the engine and transmission manuals.

My previous rig was a 38 ft 5W with F-350. Mileage was about 10-11 mpg, but it was a Montana which is one of the lighter 5Ws on the market.

The over or under variance between gas or diesel fuel prices is something that makes every RV owner want to pull their hair out. When I see diesel considerably higher than gas, I want to scream. When that is reversed, I am euphoric. You are not going to win that battle, so forget it. Get the rig that fits your dreams and lifestyle. None of them are the perfect dream, so pick the one that is the closer to it.

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Kirk
post Jan 16 2010, 09:11 PM
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While diesels do get better fuel mileage in a class A than do most gas chassis, with the huge difference in cost of the diesel units you would have to do an incredible amount of travel to save enough in fuel costs to make up the difference. Expect to pay $20K to $30K more for a diesel.


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Butch
post Jan 19 2010, 11:36 AM
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Kirk is correct as to the purchase prices as they pertain to gas verses diesel if one was purchasing new, but used this cost drops. Still the diesel units are more expensive than the gas units. We have a Holiday Rambler 37 footer with a gas engine, and we have mileage between 10mpg and mid sevens depending on the lay of the land and traffic while towing a vehicle.


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rgatijnet
post Feb 14 2010, 12:39 PM
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We had a diesel and now have a gas unit. Mileage was about the same for both units. The main reason we went to gas was because there are a lot more stations that we could get into that sold gasoline than those that sold diesel. This is not a problem if you always travel the interstate highways but we did 20,000 miles last year that were mostly on the back roads of America.
Mileage is one of those things that varies so much that there is no way to compare gas and diesel. Not everyone drives on nice flat roads with 55 MPH speed limits. If you have a lot of back country roads, and hills/mountains, you can expect your mileage to drop 25-30%. Your mileage will also drop when the winds are high, etc.
If you want to figure fuel costs for an upcoming trip, use 5MPG and at the end of the trip, if you have any money left over, go out to dinner.
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Rei
post Feb 20 2010, 04:59 PM
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From a physics perspective, diesel as a fuel is about 15% denser than gasoline, and in normal driving conditions, diesels average about 15% more efficient than gasoline engines. So a 30-35% better mpg. Obviously the actual mileage will vary depending on how much power requirements you're putting on the engine, as well as other factors (such as how well you stay within the optimal power band -- gasoline engines tend to fall off faster in efficiency outside the optimal torque/rpm envelope than diesels do).
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