I doubt theres any damage. In my years of doing this, several times I have forgotten to add mix and have run a tank of none mix thru my equip with no adverse affects.

 

I just eyeball Stabil and/or Seafoam too. Not gonna hurt a thing.

 

How many 2-stroke oils do NOT have a fuel stabilizer already in them? (yeah, prolly a can of worms)
Asking cuz I never add a fuel stabilizer, but instead make sure the tank is full (my Winterization) so there's less room for condensation. Never had any starting issues come Spring.
I use Saber at ~75:1.

 

Fuel stabilizer is a waste of time and money. Especially if you are actively using the equipment. Obviously, if you are going to use stabilizer, add it to the gas can, not the individual fuel tanks. Just dump out the old fuel and add fresh premix vs. using fuel stabilizer.

 

Also worth mentioning that ethanol free fuel is a better bet when storing any engine via Winterization or otherwise.

 

If you were to run the STIHL Ultra, you'd have the stabilizer already in it.

 

I start all of my power equipment the 1st weekend of the month, year-round and run it up to operating temperature... I also use Stabil. Maybe I'm anal?? I dunno, my stuff starts every time!! How much does it cost to treat your fuel?? Pennies... but then again, maybe I'm overly anal. My chainsaws always fire by the 3rd pull. I have one I haven't used for several years, after a year I dump the gas, put in new treated alcohol-free gas and start it once a month. Cheap insurance, peace of mind.