Diesel fuel refiners begin altering their formulas each fall to meet the operability needs of diesel engines during cold weather conditions. This change is in response to diesel fuel’s tendency to gel in the winter, caused by the paraffin wax content that is inherent of crude oil. Essentially, refiners work with a variety of formulas, otherwise known as streams, to arrive at a workable use of diesel fuel for their winter blend.
The addition of solvents and lighter fuels affect the Cold Filter Plug Point (CFPP) or Pour Point (PP) suitable for winter use of diesel fuel. Unfortunately the process to remove the wax content also significantly drops the cetane content, and this is what affects the fuel mileage of the diesel engine. Cetane, just like octane in gasoline, increases the volatility of diesel fuel in measurements of British Thermal Units (BTU). Ultra Low Sulfur Diesel (ULSD) typically contains up to 140,000 BTU’s with a centane number averaging 46 points. However, lighter fuels like kerosene range between 130,000 to 135,000 BTU’s. When added to the refining process to remove wax from the fuel, kerosene inherently drops the centane content of the diesel fuel, thus giving poorer performance to diesel motors and lessening your winter driving MPG’s.
Unfortunately, there is no curbside cetane tank test on the market today but don’t let that fact keep you from taking steps to increase your stand alone pumped diesel cetane number. Adding a cetane booster to your tank can increase your MPG during winter use. Keeping in mind that the current ULSD ATSM requirement for cetane is 40 pts, (remember the average is 46 points) it becomes imperative that diesel owners take steps to improve the cetane in their tank with over the counter additives, especially during winter driving conditions. The gains to be realized will be increased MPG up to 5%, faster cold starts, cleaner burn, less power lag, decreased ignition delay, and decreased engine noise.
Make certain to record the cost per treatment and the miles logged prior to treatment compared to after treatment. This will establish your price point to determine your savings in MPG gained.
Also, don’t neglect the other tried and true methods for increased fuel economy during winter driving, such as plugging in your truck to warm the motor prior to start, checking tire pressure, using synthetic lubricants, limiting idle time, and avoiding snow/ice conditions that reduce traction and increase rpms.