Bluestream, the ideal storage/fogging oil is one that is:
1) Easily distributed
2) Leaves a coating on metal surfaces to protect them from corrosion
3) Will burn off cleanly when the engine is started.
MMO is just about ideal for this application ... followed by a TCW-3 2-stroke oil (low/no metallic additives).
Engine oils are specifically formulated not to burn off easily and they have some metallic additives (moly, zinc, phosphorous, etc ....) which could foul-up emissions equipment, sensors, spark plugs, etc ...
Sounds like you have been getting away with it to date OK ... but as others have said, there are better products for this application ... and they don't cost much more.