There are many different engine lubricants available on the market. This can make it hard to determine the good from the bad. Quality oils will have certain characteristics no matter the brand. For instance, quality oil will be made from polymers that are resistant to breakage under extreme circumstances. These additives protect an expensive engine from corrosion, rust, and sand particles.
Quality oil should be thick and viscous. The oil needs to cling to engine parts when running, but also flow to the lowest parts of the engine to coat rings and bearings. Personally, I go for Yamaha oil as I know that whether I need two stroke or four stroke oil, their brand delivers quality.