Sorry in advance for my ignorance. #1 I know I can split operating costs with friends that I fly with, like for fuel and oil. Can I include an engine reserve charge? I think hangar/non-destination parking and insurance reimbursement are no-nos. #2 If I have friends that want to borrow my plane and I don't go with, can I charge them an engine reserve, or would that be considered rent? I want to avoid any added rental regulation compliance issues or insurance concerns. I want the plane to continue to fly during periods of long inactivity. The 2 guys who would use/borrow the plane are happy to pay fuel and oil. I'm not looking to turn a profit, but don't want to stuck with a big accelerated overhaul bill.