Diesel fuel compositions

Abstract

The use of a detergent-containing fuel additive in a diesel fuel composition, for the purpose of reducing engine power loss and/or reversing a previously incurred power loss, and optionally also for reducing smoke and/or particulate emissions. Also provided is a method for assessing the performance of a candidate diesel fuel composition based on its ability to reduce or reverse power loss, and a diesel fuel composition containing a detergent at an active matter concentration of between 100 and 500 ppmw.

What is claimed is:  
     
         1 . A diesel fuel composition which includes a major proportion of a fuel for an internal combustion engine of the compression ignition type, and a minor proportion of a detergent-containing additive, wherein the active matter detergent concentration in the composition is between 100 and 500 ppmw.  
     
     
         2 . A diesel fuel composition according to  claim 1 , which contains reaction products of a Fischer-Tropsch methane condensation process.  
     
     
         3 . The use of a detergent-containing fuel additive in a diesel fuel composition, for the purpose of reducing subsequent power loss in a diesel engine into which the fuel composition is introduced.  
     
     
         4 . The use of a detergent-containing fuel additive in a diesel fuel composition, for the purpose of reversing a previously incurred power loss in a diesel engine into which the fuel composition is introduced.  
     
     
         5 . The use of a detergent-containing fuel additive in a diesel fuel composition, for the purpose of reducing smoke and/or particulate emissions in a diesel engine into which the fuel composition is introduced.  
     
     
         6 . The use according to  claim 3 , wherein the fuel composition contains reaction products of a Fischer-Tropsch methane condensation process.  
     
     
         7 . A method of operating a diesel engine, and/or a vehicle which is driven by a diesel engine, which method involves introducing into the combustion chambers of the engine a diesel fuel composition according to  claim 1 .  
     
     
         8 . A process for the preparation of a diesel fuel composition according to  claim 1 , which process involves admixing a major proportion of a diesel engine fuel with a minor proportion of a detergent-containing additive, the minor proportion being sufficient to give an active matter detergent concentration in the fuel composition of between 100 and 500 ppmw.  
     
     
         9 . A method for assessing the performance of a candidate diesel fuel composition, comprising the steps of: 
 1) measuring power output for a diesel engine running on a standard diesel fuel composition, which standard fuel composition contains less than 50 ppmw active matter detergent;    2) subjecting the engine to a first driving cycle by running it for a first number of miles on the standard fuel composition;    3) measuring engine power after the first driving cycle;    4) calculating the reduction in engine power during the first driving cycle;    5) provided that significant power loss is observed during the first driving cycle, subjecting the engine to a second driving cycle by running it for a second number of miles on the candidate diesel fuel composition;    6) measuring engine power after the second driving cycle;    7) calculating the reduction in engine power (if any) during the second driving cycle; and    8) if applicable, calculating the extent of engine power recovery during the second driving cycle.    
     
     
         10 . A method according to  claim 9 , wherein engine smoke and/or particulate emissions are also measured and compared before and after the first and second driving cycles.