[hharney]

The engines on the 337 are not on a slant or angle. Yes, the dipsticks should be verified for calibration but do it when the oil is cold. Who checks the oil when it's hot? 99% of the time you are pulling the dipsticks before the flight not after the flight. Most engine systems will tend to stabilize to a level and stay there unless there is some kind of problem that consumes oil. Once you allow the level to stabilize after a couple hours of operation then that is a good indication of where you should allow the oil level to remain to avoid any blow by that make a mess on the airframe. My normally aspirated engines stabilize at about 6 to 6.5 quarts. That's where I operate them, remember there is one quart in the filter that is not indicated on the dipstick.