A few years ago I was underemployed. I could not always afford to fill my oil burner tank. The local fuel oil dealers charged a stiff premium for small deliveries ( cannot blame them, they have to stay in business ) I started buying 25 gallons of off road diesel when I got paid and dumping it into my tank. I live in a farm community so off road diesel was cheaper than heating oil most years. The heating oil dealers have to maintain a specialized truck and carry lots of insurance. I had my old Toyota and 5 cans. The heater ran fine and I could not tell any difference.
A lot of folks are underemployed nowadays. I thought this might help someone.