Cetane Rating (Ether)

The delay between the time the fuel is injected into the cylinder and ignition is expressed as a cetane number. Usually, this is between 30 and 60. Fuels that ignite rapidly have high cetane ratings, while slow-to-ignite fuels have lower cetane ratings. A fuel with a better ignition quality would help combustion more than a lower cetane fuel during starting and idling conditions when compression temperatures are cooler. Ether, with a very high cetane rating of 85-96, is often used for starting diesel engines in cold weather. The lower the temperature of the surrounding air, the greater the need for fuel that will ignite rapidly. When the cetane number is too low, it may cause difficult starting, engine knock, and puffs of white exhaust smoke, especially during engine warm-up and light load operation. If these conditions continue, harmful engine deposits will accumulate in the combustion chamber. Pressurized cans of starter fluid are available in emergencies, but are not desirable, because they tend to dry out the cylinders, and are dangerous if used improperly. There are also liquid forms of starter fluid available which can be added to the gasoline.