Use whatever oil you want. There doesn't seem to be any best oil. I use Mobil 2T, seems like Husquvarna Chain saw oil would be good to. Echo chainsaws are what the BME and Brinnelli motors were built from and those engines ran fine as chain saws on Chainsaw oil. Those engines are run full load, bogged down with poor cooling etc, and last for years. Mix the oil at the ratio recommended by the oil company and choose an oil that recommends a ratio close to what your engine manufacturer recommends, somewhere between 32:1 and 50:1 and tune the engine to within 100 rpm of peak on the rich side. Disassemble every 100 hours or once a year and see how things look.