We have 100 gallon Transfer Flow on our truck, came with it when I purchased it. So far its been excellent. When the main tank draws down to ten gallons, I believe, the transfer starts and pumps ten gallons or so into the main tank. I have a small display in my truck that shows how much diesel is in the main tank, aux tank and both combined. The OEM gauge will show how much is in the tanks combined. Learned that the hard way when I stopped the first day to fill up as gauge showed quarter tank and and would not take ant fuel. Played with that for ten ,minutes before another guy came over and showed me how to read the gauges. Felt.time a drum arse.:S
