When googling 4 cycle trimmers there is no mention of a 4-mix engine. They all use separate oil and gas. Maybe thats because Stihl's 4-mix is such a recent addition to the market. So, is Stihl the only company offering a 4-mix engine?
#2
ILENGINE
No, echo-shindaiwa also have 4 stroke engines that use the 2 cycle mix.