From the "Sprinter store" Sprinter Fuel Tank
Auxiliary Fuel Tank:
Our 17.5 gal auxiliary fuel tank is designed for the 07 and newer Sprinter Vans and our 13 gal auxiliary tank is designed for the 07 and newer Sprinter Cab Chassis and Class C motorhomes. Depending on mpg, you can extend your driving range to over 800 miles on the vans and 575 on the motorhomes! The tanks are Aluminum and act as an extension of the factory tank. There are no fuel level floats or auxiliary fuel pumps to hassle with. The tanks have internal baffles to reduce fuel sloshing and has a drain plug, which can be removed to insert a fitting for an additional fuel outlet. Installation is simple and takes about 4-6 hours. You do need to drop the factory tank and you must cut into the factory fuel tank to establish the cross over between the two tanks. Other than the fuel level dropping much more slowly, the factory fuel gauge functions normally. The last 1/4 of the factory tank registers and drops normal, and the 5 gallon reserve light functions normally. When filling the tanks, the last 6-7 gallons fill more slowly than 35 or so gallons. If you park nose down or drive down a steep incline for more than few minutes or so, fuel from the auxiliary tank (depending on its level) may/will fill the factory tank. Because of the one way valve at the fill neck just inside of the tank, the fuel will not go back into the auxiliary tank and the fuel gauge will reflect that.
The kit is special order and build time is approximately 3-4 weeks (sooner depending on our schedule). We do require a 50% non-refundable deposit to get the order started. The 144" 3500 Van tank is slightly different in length and has a 16.5 gal capacity. The 54"x12" area on the outboard side of the factory tank must be completely open and unobstructed for the tank to install properly. A 27 gal tank is available but requires installing a transfer pump and optional fuel level sending unit (call for estimates). Our auxiliary tanks are well designed and well made but are considered for off road use only. These auxiliary fuel tanks are not DOT approved. The 18.5 gal fuel tank is now available for $1495.00 plus shipping and handling and the 13 gal fuel tank is $1495 plus shipping and handling.