Welcome on the forum mate!!
Well if you mix fuels yourself the engine can suffer abit. All I use is this:
STIHL Power tools
When I call my dealer for a new saw, he's used to the fact that he must fill it with motomix instead of the fuel they mix themselves (they must deliver the saw in ready to use condition = stihl policy) . In the beginning he filled it with wathever crap they were using to get it running for a few minutes, and then I poured it out again and filled it with motomix.
We buy it in barrels of 200 liters. Of course that's too much for you, but it'll hold at least 3 years and you don't have to mix it. It isn't cheap though, but normally it would cost less where you are then here.
It comes in quantities of 1 liter bottles, 5 liters, 25 liters, 60 liters, and 200 liters.
Gotta tune your carb a bit so that it runs good, but hell... I may drop dead here this minute if one of my 38 stihl machines malfunctioned EVER, and we use at least three of them every day. I swear by it. Your saw will perform much better, engine will last longer (and so machine lasts longer),the burn in the cylinder is WAY CLEANER and therefore the piston and cyl will stay clean, fumes are nihil... You'll smell it at first but that goes away after a while. And it's better for the environment... You will not get tired and suffer from headaches when standing in fumes coming from the exhaust all day... Tons of pro's, only contra is pricing.
When buying this in barrels you can get a good price though. If you add it all up, I can guarantee it's even cheaper then fuel mixed by yourself.
AND CLEAN YOUR AIRFILTER REGULARLY(EVERY WEEK AT THE LEAST on regular use). DON'T WAIT UNTILL THE FILTER AND CARB IS CLOGGED WITH SAWDUST. Good maintenance WILL save you money, effort, and time... and therefore again money...