So I was thinking about Don's "missing fuel" - and I realized that for at least half the planes I've owned (including the current two) I didn't know the REAL capacity.

I know what the book says, but I never drained them and refilled them. The current two are both bladder systems, which means they're much more likely to have lower capacity than wet wings.

How many of you have drained and refilled all of your tanks to find your real capacity? Who knows, on that last flight where I landed with an hour of fuel - maybe it was only 10 minutes.