Can I put these directly over the grass? I would like to then park my car on top? Please let me know if they can withstand that?

You can install our Rugged Grip-Loc Tiles over grass. When placed over grass, the tiles may sink into the soil when the soil is wet. The tiles will hold up to a car being parked and driven over them. They are made from the same material all of our hard plastic garage tiles are.