This paper presents an investigation into the feasibility and potential advantages of a small scale Miller cycle natural gas engine for applications such as domestic combined heat and power systems. The Miller cycle engine is compared to a standard Otto cycle engine using cycle analyses and multidimensional simulation, and basic engine design implications are discussed. It is found that the Miller cycle engine has a potential for improved fuel efficiency, but at the cost of a reduced power to weight ratio. A fuel efficiency advantage of 5 - 10% compared to a standard Otto cycle engine appears possible, however it is stated that further investigations. in particular into the topic of engine friction, are required in order to validate the findings. (C) 2008 Elsevier Ltd. All rights reserved.