I like to use one fuel for all my saws, that save a lot of hassle. How many old saws are still in fine condition 40 years on (ok not used 6 days a week in a forest) I have a few so I know. Years ago I used what the dealer sold that was oregon 2t then I used husqvarna oil and with both I never had any problems and the saws are still running to this day. Then I got a 4mix, that bloody thing drive me nuts. I used ultra in that as stihl recommends and it was always full of oil and carbon, yes it was set right and run great but never a clean engine. When Aspen came out and started using that, expensive yes but not for me, my saws sit on the shelf more than they are used these days so leaving that fuel in them and knowing they start next time saves me in the long run. Now I am experimenting with aspen4 and adding my own oil, putoline mx9 (you can all scream but try it first) yet again it is not a cheap oil but very good and clean burning. Plus it smells nice and nothing like ultra.
I have never seen or heard of a bottom end failing, it's always a piston that's scored to the verge of seize. And a lot..... I would say a very high number of these are cause by a blunt/dull chain and an owner who just keeps pushing to finish the log pile. Many of theses dont understand what's going on so a fast reving engine must mean I'm cutting wood quicker....right!!
I have repaired many saws that have been run not as instruction in the manufacturer's owners manual tells them. Fuel put in the saw then a very carefully measured amount of oil added (that will do) so the horror begins, start the saw straight into wood screaming with a dull chain and when things don't work there is a barrage of things like, never buy that make they are all crap, them chains are useless and that oil is rubbish. Some dont even know how to check a chain oiler is working.... I'm not saying anyone reading this is like that but they are out there, with a voice and sadly some listen to them.
I have seen so many videos with wet pistons and "dry" bottom ends yet they (most) still run! With engines reving at 10k plus it wouldnt take long for a bearing to fail, yet they keep on going even though we are told the bottom end is dry. Which bring me to the words of a very wise old man who once told me "a little oil goes a long way"
I could go on but will leave the thinkers to do the thinking and the sheeple to carry on as they will no matter what some say because they have made their mind up and nothing will change them.
All oils work, some I wouldnt even look at and my saws are looked after and not abused so I use what "i" thinknisbthe best. I could go back to oregon 2t and they would perform just as good probably but for now I'm doing my own experiment with mx9 and to me it's looking good.
If you read this far you deserve a medal, sorry to bore anyone else. Stay sharp....stay safe.