For example, this is my
oil pan:
https://www.cantonracingproducts.com...-race-pan.html
and Canton says the system capacity is 8 quarts. So, the pan itself holds 7 quarts when full and 6 quarts when it is one quart down. When I level the pan by jacking up the back of the car and pour 6 quarts into the pan it will come up to the ADD mark. When I do not have the jacks under my car levelling the pan, the marks are about 1/3 of a quart off from true. So, if I fill the
oil up to the FULL mark I'm really 1/3 of a quart over. When I would do that the
oil consumption would initially be higher and then slow down considerably after about a half quart or so. So now I run with my oil level at the true halfway mark and I have very low oil consumption. And it took me years to figure that out.