Hardware differences between the 2.2-liter (L61) and 2.2-liter (L42) are entirely in the cylinder head and fuel delivery system. CNG does not have the lubricating properties of liquid gasoline, and it tends to produce more surface erosion than gasoline as it flows into the combustion chambers. To ensure maximum durability with CNG operation, the engine has unique valve seats and intake valves that are more resistant to erosion. The seats are manufactured from an alloy called Brico 3010, a sintered powder metal with higher chromium, tungsten and copper content than the alloy used for the regular gas version's valve seats. The engine's intake valves are forged from a premium alloy that includes tungsten, vanadium, manganese, and silicone, and has more chromium than conventional iron-alloy valve material. These alloys virtually eliminate the possibility of valve face and seat erosion with CNG operation.