A lot of folks who are new to RVing with a motorhome, especially large diesel pushers (DPs), have questions about where and how to get fuel. Most DP owners I have met have said that they prefer to stop at mainstream places like Pilot/Flying J's, Loves, or a TA Travel Center.
If you have a large DP or are planning to get one, the first thing you need to realize is that you are now as large as many semi trucks on the road. In fact, if you're towing you may be longer than a lot of them. It's clearly unreasonable that you should have to thread your way around the outside lanes of a BP or Shell station that happens to sell diesel in an outside lane. When you're towing, you can't back up - which makes it all that more complicated.
The best solution is to simply go where the truckers go. Don't worry about whether or not you're "allowed" to do it or if truckers may not like it. You have every bit as much right to stop there and fill up as anyone else.
Finding a Place to get Diesel
Many apps (like Allstays) and GPS units (like Garmin and Rand McNally RV devices) can display icons for upcoming fuel stops. The most popular places for RVers, like Pilot/Flying J and Loves, are easy to see when you use them. Other apps, like Trucker Path, can show you many more places to stop. The main problem with just telling your RV GPS unit to look for the next fuel stop is that it will most likely point you to a regular gasoline station; none of the popular apps or GPS's have a filter to display only places that have diesel fuel.
Of course, there are signs along the roadway. These are usually quite sufficient if your low fuel light isn't on. Most diesel RVers I've talked to say that they start looking for a fill-up when they have between 1/4 and 1/2 of a full tank. In my case, I start looking when I'm about 50% full.
Pulling up to the pump
Just follow the signs that truckers might follow; easy because they usually have only two things on them: "Trucks" and an arrow pointing the way. Look for an open lane like you'd do at any gas station, but know that you may have to find a lane and wait behind someone. If you do have to wait, it might quite a bit longer than would with a car because it simply takes longer to fuel a large truck; sometimes, a driver even takes time to go into the cashier and/or wash their windshield.
Some places, like Flying J's, may have big signs telling RVers to pull into lanes specifically for them. Don't do it. Remember that a lot of RVs are smaller than yours. Even though it's a special RV lane that you may be able to get into, you might find it somewhat difficult to get out.
Once you have pulled in and are sure that your fill is close to the pump, turn off your engine.
A common question asked on Facebook forums is whether or not to turn off LP gas when refueling. I'm not advocating what's right or wrong, but will tell you that an overwhelming number of people will respond with NO; they don't turn off the gas when refueling.
If you don't have a credit card that is specific to the place you're fueling (like a Pilot/Flying J credit card), you'll probably have to go inside before you pump to get your card pre-approved. Be sure to know your pump number before you go inside. Have a rough estimate of how much you'll need to charge so that they can pre-authorized that amount. If I think I may need between $150 and $200 of fuel, I'll hand them my credit card and tell them "$200 on pump 26". If I also want to get DEF (see below), I'll say "$200 on pump 26 for fuel and DEF". They'll run the card and hand it back to me.
Next, walk back to the pump and fill your diesel fuel like you do at any gas station. Note that it comes out a lot faster than a typical car pump. Even though they usually have auto-stops, they fill so fast that they ALWAYS stop and spill over to the outside of my coach, coating my paint beneath the fill. If you hear it getting near full, you can manually stop it or at least set the auto-stop to a slower setting.
If you need more fuel than the amount you authorized, the pump will stop at the authorized amount and you'll have to go back in for another authorization if you want more. More typical is that you'll use less. They will only charge you for what you use.
Next, if you need DEF, get it.
DEF: Diesel Exhaust Fluid
Quite a few of the truck stops also offer DEF at the pump. If you haven't bought your diesel pusher yet, DEF is another fluid that all diesel RVs since about 2012 are required to use. There's a separate tank in your rig that holds the def and it also has a separate fill port (or two). You might use about 1 gallon of DEF for every 50 gallons of fuel. For a large motorhome, your DEF tank may hold about 10 to 14 gallons of DEF.
Large motorhomes usually have the diesel fill on the driver's side. Some have dual fills, with one on each side of the coach. For DEF, it's convenient if the fill is on the driver side - but it's often located near the engine on the passenger side of the rig. Since DEF and diesel fuel are offered from the same pumping stand, it would be great if the DEF fill was beside the diesel fill. But life isn't that simple, is it?
For those of you who, like me, have DEF fills far away from the diesel fill, here's a suggestion: carry a couple of DEF containers that you can fill at the pump and take to your next campground. Then fill the DEF at the campground. This way, you won't feel the need to do all kinds of odd things (while truckers are waiting and watching) at the pump.
Beside all of the room you have to maneuver, using the truck lanes is great because their window cleaning poles are long; it's easy to reach top of your windshield to clean it.
After you're done with everything, get in your coach, start it and move it forward away from the pump so the trucker behind you can fill up.
If you want a receipt, get back out and go back into the store to get it. If not, drive away. If we want to get a drink or some food, we'll usually fill and then pull around to one of the large trucker parking spaces. That way, we can take our time inside.