Tenants moving in, how to handle oil currently in tank

[Carl C.]

We have tenants moving into our latest house on June 1. They are the first tenants to be living there since we purchased it. There is approximately 400 gallons of heating oil in the tanks that we had to purchase from the previous owners when we closed. We are not sure how to charge the new tenants for that or even if we should charge them for it. They are responsible for all utilities per the lease however one wouldn't expect a large oil bill at the begining of the summer. Any suggestions on how folks would or have handled it in the past? In my mind we should have thought about it when the lease was signed (4 months ago) and let them know that there would be a charge for it. But we didn't so I'm at a little bit of a loss. I apreciate any thoughts you can share. By the way, this is college student housing if it matters. We converted our previous house to gas so this was not an issue. Thanks for any help you can offer.