The service is appealing to find the person responsible for an 'act of kindness' towards its staff.
At about 3am on March 20, one of their ambulance crews filled up an ambulance. But due to a problem with the fuel card, they weren't able to pay for the petrol.
While a paramedic stepped aside to make a phone call, a random member of the public paid for the ambulance's fuel.
A spokesman for the service said: " Without the crew's knowledge a member of the public paid for their fuel.
"Once they became aware they attempted to get the man's details, to arrange repayment, but he refused saying "It's the least I could do after everything you do for us."
Do you know this man? Let's get him found! The incident happened at a petrol station on Beverley Road in Hull in the early hours of Tuesday morning.