STIHL 2-cycle oils are formulated to meet the high temperatures and lean running conditions of today's innovative and technically advanced STIHL engines. All STIHL 2-cycle oils contain a fuel stabilizer for longer storage life and to prevent fuel varnishing. STIHL recommends a mix of 50:1 high quality 89 octane unleaded gasoline to STIHL engine oil. This same mix ratio should be used during break-in.