I know. Who would do something like this? But, we did. We're out working after dark and picked up the used oil container and poured some in the gas tank. We don't know how much. Maybe a pint...or a quart? We did this to a D140 lawn tractor. The mower hasn't been started since this error. What to do now....finish filling with gas and start up?? Is it necessary to drain the gas tank?? Would appreciate advice. The lawnmower is sitting there useless while my grass grows by the hour.