My Exmark Lazer Z just recently started using too much oil. After using it for a couple of hours, the oil level on the dip stick is sometimes below the half way mark. I can't find any oil leaks. Too make sure, I have parked it on the drivewway tonight. The machine has approximately 800 hours on it. If it doesn't show leaking under the machine in the morning, what might the problem be? It does seem to have the same power it always had. Your thoughts would be appreciated.