I know there's already another thread about regular gas. I was wondering the same thing about mixed gas. I have a Stihl trimmer. It's about 10+ years old (received from my father), but works as good as new. 1 gallon of mixed gas will last me 2+ years. I've been using the Stihl 2 cycle oil. Is it OK to use 2-yr old gas in this trimmer? I always shake it real well before pouring in. Or, should I only make a half batch: half bottle oil/half gallon gas? I'm on my last tank now, so I'm about ready to mix up another batch. Thanks in advance.