So the removal of the oil (stain) is a cost that the tenant needs to reimburse you for.

But have them either pay for it upfront, reimburse you or take it out the security deposit.

Maybe you could get the landlord to reimburse you or go halves on it.

If not, I'd just send the landlord a letter saying you were not aware of any fee, there is nothing in your contract regarding a fee, that since the landlord already reimbursed your security deposit, showing you owed nothing, that you don't believe you owe anything.  

If you need to provide them for your tenant pool, you should expect repair costs and replacement costs that are not expected to be reimbursed by your tenants.  

You don't have to reimburse him any rent, but just take any rent owed out of the security deposit.I just get the impression that you're looking for a fight. 

My question was more towards whether there’s something I can do to make the previous owner pay for it or reimburse me for it.

She would normally have to pay the full rent for Aug, then you would reimburse her any overpaid rent after she moved out.  

Carpets don't lay themselves.Even better if you have the original receipt - which you should have for the IRS anyway.And if the judge doesn't want to reimburse your time in a judgement, he'll just cross it off the list.

When they move out , dip the tank figure out how many gallons in the tank , reimburse them for whats there .