It depends largely on how you measure it. If you loop the return then you only need to measure the input, from the tank, and the flow will be relatively small. The other way would be to use two flow meters, one for each the source and return lines, and subtract the difference. The problem with the first is that any air that gets into the pump will get trapped there with no return to the tank. The problem with the second method is that the flow rates that you measure will be much larger than the fuel usage, combine that with two flow meters instead of one, and the accuracy of the measurement will not be very good.

In short, the type of flow meter you get will depend on how you plan on measuring consumption. Eg. case 1: One low rate flowmeter, case 2: two high rate flowmeters.

__________________
For Sale: 1982 MB 300TD
1995 Chevrolet Suburban 6.5TD

Sold: 1980 IH Scout Traveler- Nissan SD33T Diesel