SPRING 1559117 - Caterpillar

All Caterpillar ProductsBecause of current fuel distribution problems, the No. 1 Diesel Fuel needed for operation in cold atmospheric temperatures will be available only in limited quantities in many areas. For this reason, it will be necessary for many customers to use No. 2 Diesel Fuel during operation in cold temperatures. No. 2 Diesel Fuel is a heavier fuel than No. 1 and this can cause problems with fuel filters, and possibly with fuel lines, fuel tanks, and fuel storage. For assistance with these problems, this article gives some general information about fuel characteristics that have an effect on operation and performance in cold temperatures, and what can be done to keep fuel problems at a minimum. More information about fuels is available in Special Instruction "Fuels For Caterpillar Diesel Engines", Form SEHS7067. Also, an Operation, Lubrication & Maintenance Guide "Cold Weather Operation", Form SEBU5338-02 is available as a reference.
Diesel Fuel Characteristics
The primary characteristics of diesel fuel which have an effect on engine operation and performance in cold temperatures are: Cetane Number, Cloud Point, Pour Point, and Moisture Content (amount of water in the fuel).
CETANE NUMBER: The cetane number of the fuel has an effect on the ability of the engine to start, and the interval of time before it runs smoothly. Generally, an increase of ten in the cetane number will lower the temperature at which the engine can be started approximately 12° to 15°F (7° to 8°C). After the engine heats up to its normal temperature for operation, the difference between a 40 Cetane and a 50 Cetane (for example) has very little effect on engine performance. Most fuels that have a Cetane Number above 40 will permit acceptable engine starts in warmer atmospheric temperatures, or when the engine is kept warm, either in a heated room or with a coolant heater system.
CLOUD POINT: It is important to understand that the "cloud point" of a fuel is different from the "pour point", and has no relation to the temperature at which the fuel will not flow. The cloud point is the temperature at which some of the heavier paraffin components (wax) in the fuel become solid particles. This wax is not a contaminant (foreign material) in the fuel, but is an important element of No. 2 Diesel Fuel, and has a high energy content and a very high cetane value. Removal of the heavier wax lowers the cloud point of the fuel, but also increases the cost because less fuel can be made from the same amount of crude oil. Basically, No. 1 Diesel Fuel is a No. 2 Diesel Fuel with this wax removed.
The cloud point of the fuel is important because it can limit the performance of the fuel filter. Solid wax particles can fill the fuel filters and stop the flow of fuel. Since the fuel must flow through the filters to remove dirt and foreign material which can damage fuel injection components, the most practical way to prevent the problem is to