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According to the RC Showcase website, they may be the U.S. importer/distributor (not certain) of Roto, the Roto engines run on U.S. regular gasoline. They may have been changed and the website is not current. I do not own a Roto, but do have three ZDZs.

My comment about detonation v. pre-ignition was made just to clear the air a bit. I was not, and am not, certain that the terminology had not been changed over the years. They are, as you say, two different things of different causes.

U.S. regular gasolines are not junk in their intended uses.