Rolf Reitz's research interests include internal combustion engines, chemical kinetics and sprays. A major research focus of his group is the development and application of advanced computer models for the design of fuel injected engines, including diesel and spark-ignited engines. His group also pioneered a high efficiency, low emissions, dual-fuel engine technology, known as Reactivity Controlled Compression Ignition (RCCI).

Reitz' engine experiments used fully instrumented single-cylinder research diesel engines equipped with high-pressure electronic fuel injection systems. The experimental results are used to study the effect of fuel injection characteristics (such as variable rate and multiple injections) on diesel engine soot and NOx emissions, as well as to develop injection strategies for Low Temperature Combustion engines. The engine experiments also provide validation data for the computer models. The computer models have been used in combination with genetic algorithm search techniques to find optimum engine designs.