Evaluation of Faster LTFT and SFPP for Protection of Low Temperature Operability in North American Heavy Duty Diesel Trucks

Low sulfur specifications for on-road diesel fuel effective October 1, 1993, and the low aromatics/low sulfur limits issued by CARB (California Air Resources Board) in California have increased the potential for the use of Cold Flow Additives. The additives can be used in winterizing diesel fuel to minimize the need for low sulfur kerosene. However, the only widely accepted laboratory test method which satisfactorily protects actual heavy duty truck operability in North America is ASTM D4539, the Low Temperature Flow Test (LTFT). LTFT is a slow cool test often requiring 16-20 hours to obtain a result. As such it is considered to be of little utility as a product release specification for refineries and terminals. Studies intended to identify faster test methods which would closely relate to LTFT have been undertaken. Options considered were, LTFT with faster cooling rates, of 3°C and 6°C/Hr., and the Simulated Filter Plugging Point (SFPP) test currently undergoing standardisation as a new method in Europe, So far neither the 6°C/Hr. LTFT modification nor SFPP have provided a sufficiently safe indication of LTFT. The 3°C/Hr. test on the other hand fits well with LTFT and could be considered a first step towards more practicable cold flow testing. Further work will be carried out to develop a more convenient automated test for routine use, for which modification of SFPP appears to offer the most practical basis.