Used oil mixed with diesel?

[RonMar]

Not sure if helpful, but last winter tried to burn some old but unopened 10-30w engine oil in my little diesel/kerosene vented heater, mixed thinly with the diesel, and it left a mess of carbon remains down in the burner. Normally just diesel or kerosene left everything pretty clean.

Mike

Yep, motor oil needs an agressive combustion to break down. It is real tricky to get it to burn cleanly without some form of forced atomization...