With regard to the oil reading changing with regards to shutdown time, and temperature. I was always taught and I teach my students that if the engine has been run within the past 30 minutes then the reading may be low by up to 1/2 a quart not because the oil is still hot but because some is still in other parts of the engine. I also teach them if its below what the book says is the min then get it at least 1/2 quart over the min. Anybody else teach or been taught this? I never knew about the half oil certification level but that makes me feel alot better, but im not going to tell my students because I don't want them to think they can go out with less then recommended.