Having a "fleet" of vehicles with four driving age boys and a wife, I have waste motor oil to dispose. Since none of the boys know how to drive back to the store to properly dispose of engine oil, I dump the used oil from certain vehicles into the tank of my 1031. Spark ignition engine oils (S class) in 5w30 should be fine as they are low deposit, low ash types with very low ZDDP.
So far, no issues after one tank, about two gallons to 15 of D2. Cannot say on fuel economy as it has been pulling a 4500 pound trailer in town traffic.