"A quart should last the life of a YH-type pump."
If you only change it frequently enough to need 1 quart then you deserve the life span you get.before something unrelated to
My oil company claims that it is good for 2000 hour change intervals. I will be tickled pink if I can get 50 hours before something that has nothing to do with lubrication needs attention. Perhaps I'll change the oil then or if it's something like a burnt-out motor I'll junk it and get another. The biggest and most damaging mistake that people make with oil is overfilling or not running the machine on a dead level surface. That's how oil gets to places where it can cause detonation and carbon deposits. By the way, mine's going on to 4 years old, and the oil that's been in it since after its initial run-in period is still as clear as the day it went in. As you know, I don't use ice and I only use the pump for filling or topping off 6.8-litre bottles. I also never run it for less than fifteen minutes at a time and I always drain the coolant while the water jacket is still hot before storing it for any period of time. I have sound reasons for adhering to these procedures and so far it has worked just fine.