I have brought back engines that have been siezed using WD-40 or Diesel fuel. If they were in good shape when parked, they generally free up and work decently. Not like a rebuilt, but probably as good as they were when they were parked. Now, if it is somewhere with real dampness, not just high humidity, but a wet building, corrosion could have an effect on the parts, and all bets are off on that situation.