I only mix a gallon at a time. I put a fuel stablizer in the mix even though the oil, Stihl, has a stablizer. I had the plugs foul up on my chain saw a few years ago which I think was due to old fuel. I now only burn the mix if it is no older than a month or so. I only buy Premium gas as well.
If it is too old to run in the Stihls I store it until I take it to the dump where they collect gas, oil, paint, etc.
Its just not worth trying to save a few dollars of old gas if I have down time getting the saw to run. Nor will I risk the car engine with the mix for a dollar or two of gas. I doubt it would be a problem to run such a small amount of mix in a full take of gas in the SUV but I have to take old oil to the dump anyway so taking old gas just is not a big deal.
Later,
Dan