A friend of mine just received the new version of this engine which has the Falkon ignition. It too has conflicting documentation. One paper lists premium and the other says regular. For myself, it is a matter of convenience since I have RCS and ZDZ engines. The ZDZ says premium throughout. It would be much easier to carry one type of fuel supply. As for my friend, this is his first gasser so he is trying to ensure he has everything correct from the beginning.