Fuel dilution is one of the phenomena requiring attention in direct-injection engines. This study examined the factors contributing to increased fuel dilution in direct-injection and conventional multipoint injection gasoline engines, focusing in particular on fuel dilution in the oil pan. The results showed that fuel dilution is affected by fuel consumption, fuel properties and oil/cooling water temperatures in multipoint injection engines. In addition to these factors, fuel injection timing is another factor that increases fuel dilution in direct-injection engines.
Study of Fuel Dilution in Direct-Injection and Multipoint Injection Gasoline Engines
Sagawa, T., Fujimoto, H., and Nakamura, K., "Study of Fuel Dilution in Direct-Injection and Multipoint Injection Gasoline Engines," SAE Technical Paper 2002-01-1647, 2002, doi:10.4271/2002-01-1647.