A fuel composition and method for cleaning up internal components of a fuel injector and for improver injector performance for a diesel engine. The composition includes major amount of middle distillate fuel having a sulfur content of 50 ppm by weight or less, and from about 1 to about 30 ppm by weight based on a total weight of fuel of a fuel soluble hydrocarbyl sulfonic acid or salt such as an alkyl aryl sulfonic acid or salt thereof, wherein the alkyl aryl sulfonic acid or salt thereof is effective to improve injector performance.