With the popularity of 4-stroke engines over the past decade, protecting a motor with fogging oil is more important than ever because of the many steel and cast iron parts used in their construction. There are always valves open to the atmosphere where moisture in the air condenses on the finely machined metal parts during temperature changes and causes rust and pits. Unlike the old traditional carbureted 2-strokes whose components normally have an oily residue, the 4-stroke steel and iron parts are subject to corrosion damage, more so in salt water areas. Valves, rings, and cylinder sleeves are the most prone to rust and in some motor designs, a stuck valve can be hit by a piston causing expensive damage when the engine rotates when starting. Rust buildup on the cast iron bores gets scraped away by the piston rings as the engine starts removing small bits of metal that changes the clearances between the pistons and cylinders each time it happens. Problems such as lower compression, poor idle, and/or increased oil consumption with high increases of hydrocarbon emissions are possible as cylinder and ring wear occurs.