Dollar seems start to enforcing a new policy. You must present gas receipt upon return.
I was at Charlotte last week. Return agent demanded my gas receipts. Then she determined the gas station could be 10 miles away and must charge me 2 gallons of gas ($10). Ridiculous policy !!
I fought it off but may use Dollar only as a last resort from now on.
A co-worker said Dollar at Greensboro also has such a policy. AVOID THEM!!