The only thing I can think of, is there might be a 'bridging' issue with the coal feeding down the hopper. Its a fairly small opening going to the pusher-bar and if I fill the hopper with damp coal, it will stick together and form a 'bridge' at the throat, and not fall down to the pusher-bar until I push a poker down thru the coal and it collapses the bridge. Oil will make the rice sticky, so you may experience this bridging issue.
It does measure air pressure/vacuum and exhaust heat temp.
If the oil residue were to clog/cover a sensor, it might have an issue operating correctly.... Dunno
That would take an 'ell of of alot of oil....