Most cooking oils will be subject to emulsification when H2O is added and vigorously mixed, creating a salad dressing( add the vinegar for flavor). While it will separate over time when undisturbed, during the running period the oil is severely compromised because of the H2O mixed into it. one would not want H20 in their crankcase oil, same idea.My personal favorite lube for models is Mercury 2-4C grease. It is waterproof, contains telfon, remains stable thry a very wide temperature range, is easy to transfer to a loading devise( syringe) and is inexpensive. One tube, and they are small tubes, has lasted my 20 years and has plenty left.