guess I assume every stihl product is the same around the US in that they all require the use of there oil mix to honor the warranty.
that's what I've always been told by my dealer. so if the OP is using the stihl bottles how can it be mixed wrong. you add one bottle per 2 gallons of fuel. now I don't actually measure it and I error on the side of having a little heavier on oil than fuel in the mix.
but true he could try that first but I wouldn't go taking things apart myself. let the dealer do that.