The introduction around the world of low sulphur diesel fuel has required extensive use of lubricity additive technology in some markets.At the same time, the use of performance diesel additives such as detergents and defoamers is becoming more widespread.The wider application of performance diesel additives demands the introduction of proven technologies in new markets, whilst new requirements are met with a combination of existing and new additive technologies. Such developments are not without risk. These new applications could generate a variety of field problems and extensive testing is necessary to prove that the use in a new environment is trouble-free.This paper illustrates how diesel fuel additives can be efficient in solving specific problems and, at the same time, can generate a host of new problems such as plugging of fuel filters, in-line diesel pump failures, increased level of engine bore polish and deactivation of other performance diesel additives.Where recognised industry tests are available, they have been used. When such protocols do not exist, in-house tests have been developed. This paper describes the engine test used for assessing the in-line pump sticking tendency of different lubricity additive technologies.