StreetStalker, There is definiely about 30 ounces of oil left in the engine of an Evo when you change oil. When I change my oil I drain the tank, and dump in 3 quarts. (motor previously warmed up). The I pull the filter, put a oil catcher that I made out of an empty gallon milk jug and let it idle until clean oil comes out where the filter goes. It usually starts to start looking clean at about 25-30 ounces. The I shut it off, install new filter and top off tank. My question is how much should I keep in the oil tank? If I fill it as per HD recommendations it always throws a little out the breather (S&S carb) and also the lower vent which is routed up and around the outside of the oil tank and down towards the frame. ( it has a one way valve in it but oil vapor builds up and it still drips when I come home from a ride. It has an S&S 107 engine so it vents from the bottom next to the oil pump as well as on top.It runs strong, and this is just a small irritation. Anybody know where the happy medium for the amount of oil in the tank should be? I am trying to figure that out now and I am down pretty close to the add mark.It is not throwing any blue smoke it just seems to send oil out of both breather vents. Thanks for any input. CAHDBIKER