RVs use more propane than a grill ever will — heating, hot water, refrigeration and cooking — so the per-gallon price you pay is a real line item on a long trip.
DOT cylinders you can take off the rig and carry to the fill station — commonly 20 lb or 30 lb sizes. The 20 lb math from our guides applies directly: about 4.7 gallons per full 20 lb cylinder. Removable cylinders need periodic recertification; see recertification & expiry.
A permanently mounted ASME tank filled in place — you drive the rig to the dispenser. These tanks are built to a different standard than removable cylinders and do not follow the same recertification cycle, but they still need to be in sound condition, and a station must refuse a damaged tank. Ask the attendant if you are unsure about your tank's status.
On a 4.7-gallon grill-tank fill, a $1/gal spread is worth about $4–$5. On a large motorhome tank taking several times that volume, the same spread is worth proportionally more — every fill, all season. Before a trip leg, check the price index for verified prices along your route, and for chains, remember the one transparency exception: U-Haul publishes a live per-gallon price on each location's own page (more than 1,500 locations offering refill and exchange nationwide, Business Wire, Oct 27, 2026), so you can price a stop before you drive to it.