in the Vehicles Fuel Logs Form
if I add 62,93 Liter and 83,00 EUR the Price Per Liter must be 1,319
but a price of 1,32 is stored. so the "on_change_" recalc the values and they are not accurate

sry guys but it makes no sense for me...if I am come from the gas station, I have a bill with EUR and Liter. I would not enter the price per liter. 

The price per liter should be always claculated with 3 decimal places and be readonly in the form

you might be able to explain it to me.
thx
fabian