Give fresh Kerosine to your wife and a glass of unknown to the mother in law wait 20 mins,then watch them carefully, when they start to run about watch and see which one seizes up and crashes use the other fluid in your tubine this contains oil.. How ever if they both stop at the same time they have run out of fuel and need a c135 to give them air to air refuelling if this cannot be called in, wait for them to crash and burn, no more problem !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
The best thing is the 2x glasses kerosine and oil will go brown in sun light.
Good luck.
MH