I am a bit confused about oil grades and types for 4 stroke Honda and B+S type engines. I have been using fully synthetic oil often of a 'better' grade than shown in the manual. Recently an experienced repairer told me to use only mineral oil as that is what they were designed for and as it states in the manual.
My questions are (i) is there a downside to using synthetic in these types of engine? and (ii) is it ok to go for a wider temperature range oil such as the 5w50 motorsport oil used in the 7. Again, what's the downside?
Many thanks, Steve