I am sure your car drips a little oil. Try letting your car sit for 5 months and pop the hood after you first start it. See if you smell or see a little bit of smoke once the engine warms up. Trust me... it is there if you look hard enough. You won't see stains on the garage floor though. But a little drip is normal. You show me a car that sat for 3 weeks and I will show you the leak
I will find it!