I run used motor oil. I just tip my oil in a 60 lt gas cylinder, and then used compressed air to force it through a filter. I cast an ally piece, (You can buy aftermarket remote filter units), and then machined it to suit my 'cruiser filters. (So I change them out every 5k and then they get reapplied to filter my burner oil).IMG_6012a.jpg
The filtered oil is pumped directly to a fuel tank that runs my (nudge) burner. I just sourced parts from the plumbing store and my own stash. Never had a problem
IMG_6360a.jpg Clean "used" engine oil, is settled. Filtered, stored, (settled again) before burning.

Cheers Phil