With the diesel emissions and fuel consumption regulations and laws being tightened up, Common Rail System (CRS), capable of accurate and high-pressure diesel fuel injection, has become very popular in the world, and this CRS market is expected to continue to grow in the future. As use of the CRS becomes widespread, CRS is supposed to be used in a wide variety of environment, e.g. bad fuel (for example, much dust  and/or water), which increases concerns of CRS reliability. In an attempt to cope with such bad fuel properties, CRS and Fuel collected from the market was investigated. And based on this result, a new test method was worked out to simulate fuel stresses in the market. This test method verified the improved design of CRS with enhanced fuel robustness. This paper describes the new test method and the fuel robustness-enhancing effect of CRS based on the test method.