We''ve never seen corrosion on new, unused engines. Corrosion almost always starts the first time an engine is run. The fuel we use attracts moisture, and combustion products do work their way into the lower-end of the engine. The combustion products are mildly corrosive. When you put them into an engine, you have a mild electrolytic solution, that combined with the dissimilar metals in the engine, will cause corrosion.

Higher-nitro fuels will give you slightly-more acidic combustion products, so you need to be more proactive when nitro starts getting above 15%-20%.

To prevent corrosion, you need to use a model fuel that is heavy on castor oil in the oil mix, or use a good-quality after-run product. A good after-run oil would be red automatic transmission fluid, air-tool oil, non-graphite gun oil, or any of the commercial products sold as after-run products. Be very, very liberal in your application of after-run oil. A few drops are worthless. You need to make sure that the bearings and crankshaft are well-coated. The larger the engine, the more oil you''ll need. Four-stroke engines need the oil injected into the crankcase because oil put into the carb won''t coat the lower-end. Don''t put the oil into the fuel nipple of the carb of any engine, but put it into the air passage in two strokes, or into the crankcase vent nipple in four-strokes.