I don’t have a 4 stroke auger, but I used trufuel in my auger, chainsaw and weed whacker over the last year. In the fast I was religious about getting non-oxy 91 octane, used synthetic oil with fuel stabilizer. I found that they start and run better with the tru-fuel than they did prior.
It isn’t cheap, but its convenient because the metal cans don’t seem to leak like a gas can when transporting either which is an added plus. I have a fresh can waiting to go into my auger any second!