I've never heard of it. You should be using a mid-grade (89 or 91 octane) name brand gas like Shell, Exxon, BP or some quality brand of gas. That gas you're using is of unknown origin and quality. All gasolines are not the same and I don't care who tells you otherwise. I have some very old Stihl equipment and it all runs like a top, day after day. I use Shell 89 octane. If you look in your Stihl owners manual it will tell you the minimum octane is 89.