I actually quit oiling them after they came out with the 5CP which uses the same low pressure seals as the 310 but doesn't have wicks or oiling holes. But when someone asks about oiling them, I just say what I did above because I'm tired of explaining and arguing against what it says on top of the pump. I quit trying 30 years ago when a guy asked me why his 310 oil seals kept blowing out and leaking, which was happening because 1) he FILLED the crankcase to the top because the sticker on the cap said to fill it, not to fill it to the proper level, and 2) he didn't take the sticker off the cap so the pressure from the oil expanding would blow the seals out. He never agreed that "fill with oil" didn't mean to literally fill it.