You have a good mix for break in but 20% is usually plenty for oil content. Run a few tanks of what you have through it then change the plug. If that is no help purge all the old fuel out by borrowing a 1/4 tank and run it out then borrow a full tank and re-adjust.
I spent a whole day adjusting a carb with bad fuel and all I got was Fustration. We all hve been there. Just for peace of mind CLOSELY inspect your tank set up in side and out. STUFF happens

It is also worth while to pull the needle valve out and blow some fuel through then replace the needle valve. Check the tip for defects dirt etc. this is also a good time to add a small piece of fuel line to prevent air leaking around the needle valve. Always watch for a short pulse of air bubbles when adjusting the needle valve. This would indicate an air leak around the O-ring...don't ask how I know