Briggs & Stratton engines typically recommend the use of unleaded gasoline with an octane rating of 87 or higher for optimal performance. In general, it is advisable to choose fuel that does not contain more than ten percent ethanol content, as higher levels of ethanol can lead to engine issues over time. Additionally, Briggs & Stratton emphasizes the importance of using clean fuel, free from debris and impurities, to maintain the engine's efficiency and longevity. When storing fuel for extended periods, it is wise to consider adding a fuel stabilizer to help prevent the fuel from degrading. It is also beneficial to consult the specific engine manual for any unique fuel requirements or recommendations. For more detailed information, it may be useful to refer to the official Briggs & Stratton website.