Follow your owners manual. If your auger is new, then it is specially important that you follow it. I have used 24:1 for years in my Jiffy 30, , and yes, it is smoky, and spits exhaust oil, and generally pretty messy, but that is what Tecumseh - the motor maker recommends. Next year, after you've run a couple gallons through it, you can consider
using a synthetic such as Amsoil or Opti-2 at 100:1. Just get your auger broken in properly first!
Check out the great tips under Equipment - Ice Augers below. Lots more good ideas.