The us market is one of the few where 50 to 1 is std recommendation. Other countries, specifically that dont have high emissions standards, are normally around 32 to 1. It's also been shown the cylinders, seal better at a higher ratio of oil. Carbon build up can be an issue with excessive ratios, but is more a function of what oil, and the additive package then necessarily the amount of oil. I've always been a fan of 40 to 1 myself and havent ever had carbon issues. I've also always used a quality oil in my fuel, I attribute the lack of carbon and longevity of my equipment to that. For obvious reasons we all have different preferences in how, and what we run.