I use waste oil to heat my shop as well. I have room to store about 1800 gallons. Letting the heater run at a nice temperature all winter, all day/night, I used about 700 of my stockpile. Plus the oil changes that came in through the winter as well. This was not an extremely cold winter for us in Kansas City. Very few single digit overnight temps. I would hate to see a gas bill for heating this place through normal means of natural gas or propane.