Pihutze, first of all - there is no "C172" correct dip stick! You have to specify which, as a SP will have different scales from a G. Dip stick measurements, always on both(!) tanks at prefilght check, are a good way to get to know your gauges uncertainty ... Btw, the markings are not linear on most 172s. ... and do not, I repeat do not, use a wooden stick. In old times when Avgas was all mineral that was ok, but with increasing bio-!!!! it is not advisable to grow nasty bacteria and other stuff on a wooden soil. This especially applies for those with Mogas/Autofuel STC! Go for a non biological usable substrate, i.e. a PTFE or PEEK sticks.