I have used left over 32:1 thru 50:1 gas in 4 stroke mowers for years with no ill effects. And ... no visible smoke! Some times I run it straight ... sometimes mixed with fresh gas. I have never had a problem with these fuels and there is no increase in carbon deposits in the engine. I just retired a mower that was 20 years old and oil in the gas was not the cause of its retirement ... old age was. The motor could have been serviceable for several more years.

Or like several have said, just dump it in the family truckster.