1)  The landlord may not change or add terms to a lease in the middle of it, unless there was a specific reservation of the power to do so. (e.g. there was a clause in the lease saying that the landlord could make new rules.) They of course may add new rules when the lease is renewed, and tenants who don't agree don't have to sign.2) If it can be proven that a tenant's car damaged the landlord's lot in some way beyond the usual wear and tear that a parking lot gets, then that tenant may be charged for the repair cost and it may be taken out of the tenant's security deposit. Most drippings from parked cars would probably be normal wear and tear, though its not impossible for an excessive leak to justify charging a tenant.3) The fact that a car is road worthy is irrelevant, if either there is a rule made pursuant to (1) or provably exceptional damage, etc. per (2).