Do you add oil to the gas of your Sears snowblower?

That would depend on whether the engine is 2-stroke or 4-stroke (aka 2-cycle & 4-cycle). If the engine does not have an oil filler tube, it is a 2-stroke and oil must be added to the fuel. If it has an oil filler tube, it is a 4-stroke and oil is added through the filler tube.