I'll be watching to see how you deal with the burner. I am now using some waste oil for heating, and plan an oil fired melting furnace in the near future.
Waste oil is a far cry from fuel oil, but contains no less than equal energy. It's much harder to ignite, but burns well when heated. I now blend about 10% filtered motor oil and add it to the oil supply for the boiler that heats my shop. With heating oil approaching $4/gallon, it helps keep costs in line. It does require more frequent cleaning of the burner and boiler, but that's a small price to pay if you consider the savings, which are quite substantial.
If I was able to dedicate time to a modified burner, could be I'd shift towards an even higher percentage of motor oil, but the flame characteristics are not great even with 10% with the nozzle I'm using currently.
One word of caution. You likely understand that used motor oil is anything but clean when you receive it, even if great care has been exercised in keeping crud out. I strongly suggest you build a large cone type filter, one that holds about 5 gallons of oil, and filter everything you receive. I use a double filter, one quite heavy cotton, the other a light weight cotton that catches the large deposits that accompany the oil.
Filtering doesn't happen fast, but you can filter at least three gallons daily, which should be far greater than your demand. The filter will load up towards the bottom, and not allow much to pass, but the upper three or four inches, which actually present the greatest surface to the oil, will continue to allow oil through for days on end. I gather that the contaminants tend to gravitate to the bottom, leaving the sides towards the top open.
I have been following my own advice, and the oil is clean enough to pass the filter and nozzle of the boiler with no problems. That would not be the case if I didn't filter the oil.
Keep us posted.
Harold