By Russ and Tiña De Maris
It’s a good question: With the price of motor fuel rising again, is it wise to carry full fresh water tanks, particularly when heading over mountain passes? Is there any advantage either way–full or empty?
Getting more miles out of that costly tankful of diesel or gasoline is the smart thing to do. Since it takes more fuel to push around more mass, will keeping the fresh water tank empty–or near empty–help with fuel economy? That’s a “depends” kind of question. Here’s the scoop from Uncle Sam’s fuel economy watchdogs:
“An extra 100 pounds in your vehicle could reduce your MPG by up to 2 percent.” Sounds pretty serious, with water scaling in at about eight pounds a gallon, a full 40 gallon tank coming in at over three times that weight could give you some pause. But here’s the other side of the equation: “The reduction is based on the percentage of extra weight relative to the vehicle’s weight and affects smaller vehicles more than larger ones.” If you’re tooting around in an SUV pulling a flyweight pop-up trailer, a full water tank could cause you some concern. A one or two percent loss could easily translate to the equivalent of paying four to eight cents more per gallon of fuel–for a smaller, lighter RVing combination.
On the other hand, if your rig is already a heavyweight, like a big motorhome or a large travel trailer or fifth wheel, the extra water weight may not amount to much. So what are the pluses of carrying fresh water in your tank?
It is one less thing to worry about at the end of the travel day. If you pull into camp (or your favorite Walmart on the way), you’ll know you have plenty of water to shower off the road dust with. If you fill up before you leave home, you’ll know the quality of the water in your tank, and hopefully won’t have misgivings about drinking it, either from the standpoint of taste or safety.
If you decide to forgo carrying water in your tank, where might you look for fresh water ‘down the road’? Some RVers will slip into a state park, paying the “day use fee” (if not outright staying overnight) and fill up in the park. Others look for potable water supplies where they dump their holding tanks. Be sure it’s labeled as potable though! Some ask if they might fill up at a service station or store. If you’re doing a big fill, it might be good for the RVing image to offer to pay for the fill up.