I guess it depends on the build. I’ve tried running 32:1 and unless I’m working the heck out of the saw it seems to accumulate more carbon than 50:1 - IT could be the fuel itself is causing this. While pricey, the canned motomix alkylate fuel has served me very well and I use it on my smaller (40-60cc) saws. Obviously running a 395xp on it will cost an arm and a leg so IF I have a lot of large bar work (up to 5gal) I will use pump gas and mix my own. After I’m done I’ll drain the remainder and fill 1/2 way with the motomix and run it for a few minutes to “flush” out the pump fuel. I’ve noticed FAR fewer issues doing it thus way especially if the saw is going to sit on the shelf for weeks or months until it’s next use