I have an older push mower with a tecumseh engine and it only has a yellow fill plug on the bottom of the crankcase but no dipstick. Most forum threads that I seen say to fill it to the bottom of the threads. I have found a manual online and it says to fill to the overflow hole, so my question is where does the overflow hole go? I pour in almost 1 quart of oil and the oil never overflowed of the fill hole, so where does the excess oil go?