Fuel and Lubrication
Fuel and Lubrication The only fuel used for automobile operation is specially formulated gasoline, even though diesel fuels are used for many trucks and buses and a few automobiles. The things in a good fuel for automobile are proper volatility, sufficient antiknock quality, and freedom from polluting by-products of combustion. The volatility is reformulated seasonally by refiners so that sufficient gasoline vaporizes, even in extreme cold weather, to permit easy engine starting. Antiknock compounds, principally tetraethyl lead, were added to most gasolines to prevent knocking, a rapid, uncontrolled burning in the final stages of combustion that results in a characteristic "knock," or pinging noise, and may damage an engine or reduce its performance. Small lead deposits on such places as engine-valve seats improve valve life. Antiknock quality is rated