What the POH says you'll use in fuel, what you'll use unleaned, what you'll use properly leaned will all be different.
What you will use, when you lean however you do it, and what another pilot will use when they lean will also be different (even thought it shouldn't be, experience has shown that it is).
One of the most interesting things that I did in flying, was to calibrate an accurate dipstick for the aircraft that I fly, and then use it measure my fuel consumption on each flight.
Simply dip that thanks before and after each flight and work out how much fuel you used.
Then compare that to your flight times and see what you get.
I compared it to my startup/shutdown duration, my in flight duration and my tacho movement. To my surprise it was the tacho movement that was the most consistant indicator of fuel usage.
Do the same for yourself. It won't take all that many flights (5-7) before you start to see consistant readings, and you'll be able to predict your fuel remaining to which a few litres.
It's a very enlighting exercise to do.
dp