Plasma sustained ignition systems are promising alternatives to conventional spark plugs for those applications where the conditions inside the combustion chamber are more severe for spark plug operation, like internal combustion engines with high compression ratio values or intake charge dilution. This paper shows the results of an experimental activity performed on a spark ignition internal combustion engine equipped with a Radio Frequency sustained Plasma Ignition System (RFSI). Results showed that the RFSI improved engine efficiency, extended the lean limit of combustion and reduced the cycle-by-cycle variability, compared with the conventional spark plug for all test conditions. The adoption of the RFSI also had a positive impact on carbon monoxide and unburned hydrocarbon emissions, whereas nitrogen oxide emissions increased due to higher temperatures in the combustion chamber. Therefore, RFSI represents an innovative ignition device for modern internal combustion engines and overcomes the compatibility problems of other non-conventional ignition systems. (C) 2014 Elsevier Ltd. All rights reserved.