I've only run a few pre surpass 4 strokes back then they used the same fuel with out a problem I do not have the 4 strokes you mentioned so I do not know.there is nothing wrong with using fuel with more oil you will notice that the instructions give minimum oil content but not a maximum.the nitro content affects idle performance more than anything else.try the 5% nitro blend in your engines and if it idles for you then you are all set.