RV Weight and Fuel Economy

A major item to consider in choosing an RV is weight capacity and whether it is adequate for your needs. Weight capacity for any RV (or tow vehicle) is measured by its gross vehicle weight rating (GVWR), which simply refers to the total weight allowed for the vehicle itself and anything added (this includes people, fuel, water, propane and supplies). By itself, the GVWR is of little significance. It only has meaning when it is compared to the actual weight of the unit when it's ready for use. Only then can you tell if the weight falls within the allowable limit (the GVWR) set by the manufacturer. Of course, the total weight can't be known until the fully-loaded RV is driven onto a scale, but for evaluation purposes you can make an educated guess about the usable weight capacity of an RV with just a few simple calculations.

Your weight-carrying calculations can be simplified and made more accurate by observing the unit's unloaded vehicle weight (UVW), or dry weight, and net-carrying capacity (NCC) label. All RVs manufactured since September 1996 are required to carry the new label, as specified by the Recreation Vehicle Industry Association (RVIA) for its member/manufacturers.

The UVW represents the vehicle's actual weight, minus cargo, water, propane and passengers. NCC is the amount of payload the unit can carry. Some manufacturers weigh every RV as it comes off the assembly line, while others only estimate the weight. The UVW and NCC figures may not include factory or dealer-installed options, so even these figures are not etched in stone. You still need to add the weight of the unit's fresh water and propane, and possibly motor fuel if it's a motorhome, to arrive at a reasonably accurate cargo-carrying capacity. 

* Fresh water weighs about 8.4 pounds per gallon.

* Propane is approximately 4.23 pounds per gallon.

* Gasoline weighs about 6 pounds per gallon.

* Diesel is about 8 pounds per gallon.

Use the manufacturer's fluid tank-size specifications to add the proper amount of fluid weights to the RV, by multiplying the tank capacity in gallons by the pounds/gallons figures above.

Don't forget to figure about 150 pounds per extra passenger in addition to the driver.

Some of the manufacturers seem to use a different scale than the rest of the world, so don't penalize the honest ones by not considering their products. Weight capacity costs money. To increase it requires a heavier-duty chassis, larger tires, heavier springs, etc., so manufacturers, in trying to keep prices in line, are prone to skimp a bit on extra-weight capacity. But excess-load capacity is not all good; it can make for a hard-riding RV. The ideal is slightly more capacity (a few hundred to around 1000 pounds) than needed with a normal load.

Total Weight of Rig  Gas Mileage Diesel Mileage
20,000 lbs or over 5 to 8 mpg 5 to 10 mpg
15,000 to 19,000 lbs 6 to 8 mpg 8 to 11 mpg
12,000 to 14,000 lbs 7 to 9 mpg 10 to 13 mpg
9000 to 11,000 lbs 8 to 11 mpg 12 to 15 mpg
6000 to 8000 lbs 12 to 15 mpg 16 to 20 mpg
3000 to 5000 lbs 20 mpg or over 25 mpg or over

This table may help give you some idea of fuel economy in relation to total weight.

While it's certainly not exact, it can be useful as a planning tool.

Finally, gross combination weight rating (GCWR) is the maximum total combined weight of any vehicle and its towed load, which can be a truck and trailer or a motorhome and a towed car, for example. GCWR is another figure that must not be exceeded if you are to be driving a safe, reliable RV combination. Weight also has a major influence on economy of operation, specifically regarding fuel consumption. While overall size has an important bearing on livability, it also has a strong influence on total weight. The larger the unit, the heavier it generally is, and the more fuel it will consume getting to your destination. So if you plan a lot of travel and fuel costs are important, select a smaller unit, which may also be easier to drive. 

 

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