In small engines such as two stroke engines, Opal fuel is safe to use if the manufacturer recommends the use of regular unleaded 91 as a minimum.
Testing of small two and four stroke engines, including a four-stroke generator, a two-stroke line trimmer and a two-stroke lawn mower, showed that the use of Opal fuel in small engines may perform as good as or better than regular unleaded petrol.
However, for optimum performance, BP recommends the use of premium 95 or 98 octane fuel.