Happened to me with a ST G51 after a crash about 6 years back.

I was so P-----ed off after the crash I just chucked the model on the shelf for a week without draining the motor properly and when I went to start the repairs, found rust EVERYWHERE inside the engine.

The Piston ring was seized with rust, the bearings were covered with it and there was a rust "sheen" all over the liner and crankshaft. And I was using 20% castor oil in my fuel.

Had to rebuild the motor entirely. (This was in the days when ST's were made in Italy and were a lost costlier than they are now. Nowdays it would not be economically worth doing a complete rebuild.)

It taught me a valuable lesson and I have been using After Run oil religiously ever since, whether the motor be Ringed, ABC, 2 or 4 stroke.

The only rebuilds I have done since that incident, have been as a result of crash damage or engines that are just plain worn out.

After Run oil is good insurance.