04-25-2022, 03:39 AM
Not sure this is a surprise. The donated fuel has - no doubt - started decomposing like any other fuel. But it was held in a sealed container ( unlike gas tanks in cars, m/c or airplanes or in carburetors ). So after the vapor pressure of the most volatile components had built up in the can, further loss of these components stopped.
Next, when you poured it into the tank of your mower #5 some if not all of the built-up residues stayed at the bottom of the can (I suppose you did not shake the can wildly before pouring ?). So the fuel - which worked seemingly fine in your mower - is different in two ways from bad fuel in a tank or in a carburator after 4 years. First it didn't lose all volatile components, second what fell to the bottom over the years remained in the can. In a carb it would have blocked the nozzles.
With your carb (probably) kept dry while not in use, the engine was ready, the carb was ready, and the fuel simply had less energy content (per kg or liter). Knocking would have occured with the gift fuel in larger cylinders sizes (diameter matters, not stroke) and at higher temps, but this cannot be seen in your lawn care machine.
Next, when you poured it into the tank of your mower #5 some if not all of the built-up residues stayed at the bottom of the can (I suppose you did not shake the can wildly before pouring ?). So the fuel - which worked seemingly fine in your mower - is different in two ways from bad fuel in a tank or in a carburator after 4 years. First it didn't lose all volatile components, second what fell to the bottom over the years remained in the can. In a carb it would have blocked the nozzles.
With your carb (probably) kept dry while not in use, the engine was ready, the carb was ready, and the fuel simply had less energy content (per kg or liter). Knocking would have occured with the gift fuel in larger cylinders sizes (diameter matters, not stroke) and at higher temps, but this cannot be seen in your lawn care machine.