Your engine needs oil when running. You want it full when warm, after running. Why? If the level is too high, the crank and rods will foam the oil, and foam does not provide good lubrication. If it too low, well you can figure that out for yourselves. Granted, there is a allowable level change, but it is better to operate on the upper end, than the lower end. Sudden movements of the vehicle can cause the oil to flow away from the pickup. Remember, when oil is up in the engine, it is not available for being fed to the rotating assemblies. If it is at the full mark, or just below, it is better than being at the ADD mark when cold. Remember back in the 70s and 80s when the ski boat era was all the rage. I can't remember how many engines came into the shop, under warranty, that were completely turned to junk. This was caused the operator weaving back and force at high speeds. The only real fix was a dry sump oiling system.
