In particular, it's valuable to have good 1-gallon marks on the nose tank gauge.
I was astounded when testing mine that it took several gallons (3.5) before my particular float gauge came off the bottom. DO NOT fly based on my number but DO measure the status with your own float gauge. Similarly, any filler-cap-mounted float gauge in the wing tanks will only be able to measure the top half of the tank. Even the built-in gauge shows empty 3-4 (or more) gallons before the tanks are empty, depending on the exact nature of the float, whether it's saturated, etc. Doing a slow, tedious test is IMHO really worth the time and effort. I'd do one gallon at a time for the nose tank then two gallons at a time for the wing tanks. Ed
