I have a Sthil FS90R 4 stroke 28cc and it’s around 10 years old or so, but still works like a champ. I liked the 4 stroke engine so much that I bought a bigger FS111RX 4 stroke 31.4cc today. Even though they both are 4 strokes, they have no oil sump and still uses 50:1 gas/oil mix. I also put on another Echo Speed Feed 400 on the new one I got today and ordered another handle extension. The handle extensions are the best money spent on an accessory! It allows you stand straight up and adds to the handling ability and accuracy. Highly recommended! And the speed feeds makes loading new line a breeze.
https://www.sawsalvage.co/collections/echo-trimmer-heads
Speed feed heads are great. I found this place a while ago, they are cheaper than anyone else. I have ordered from them.