In the Navion I have pretty accurate analog fuel gauges and also an EI fuel flow meter. The meter has proved to be very accurate. If there's a discrepancy I figure it's due to varying tilt when fueling.

 

  Just the same, I don't trust it or the gauges. The fuel flow won't show you if a sump drain or any part of the fuel system starts to leak. I'm constantly thinking about fuel levels and cross-checking between the gauges and the totalizer. If I switch to tip tanks I time each one as well because the excess fuel is returned to the main tank. If a needle seems to drop too quickly compared to what I expect I get very focused. When switching I set the fuel flow on pressure indication- a drop provides enough warning to switch back quickly if there's air in the line.    -Bill Wade