The answer is the Clarity does NOTHING to detect old gas. I know this because my wife's Clarity burned so little gas that after 13 months the tank still showed full (not a single bar dropped). When I asked my dealership service department they tried to tell me the Clarity burns gas anytime you go over some predetermined speed - in other words they thought it was a gas/electric hybrid and not an electric/gas hybrid.I don't think we really know what Clarity does if the gas gets really old, say over a year,
Edit: My Volt went 345 days before it entered Fuel Maintenance Mode. I burned through all the gas (as in ran the tank dry) and then put $10.00 (2.8 gallons) of gas into the tank.