My 22 horse motor on my John Deer mower tractor keeps showing a rising oil level check without adding any oil. I think I can smell gas in the oil. How does this happen and what should I do about it? I've been draining some oil out when it gets a little above the full marks. I drain it below the full level and add a little fresh oil to keep the viscosity from getting too thin. At first I thought it was condensation build up, but it isn't frothy and I drain the oil in a jar and let it set to see if the oil showed any floating on top of some water. I see no such thing happening, so I'm pretty sure it's mixing with gasoline.