Good tips from above, and also empty and clean out the gas tank. Don't use stale gas/oil mix. It's worse than ever with todays ethanol gas.
Phase separation,
In the case of two-stroke4
engines, this water-ethanol phase will compete with the blended
oil for bonding to the metal engine parts. Therefore, the engine
will not have enough lubrication, and engine damage may result.
In the case of four-stroke engines, the water-ethanol phase may
combust in the engine. This combustion can be damaging to the
engine because the water ethanol phase creates a leaner
combustion mixture (i.e. air to fuel ratio is higher than ideal).
Leaner mixtures tend to combust at higher temperatures, and can
damage engines, particularly those without sensors to calibrate
air to fuel ratios.
Phase separation, happens when the ethanol bonds with water and settles out of the gasoline to the bottom of the tank leaving the oil behind.
Can old gas be the cause of a blown engine? Answer: YES!!! It was a test question in marine tech school, years ago.
Two reasons, lack f lubrication, and as mentioned above, a lean gas to air mixture creating higher than designed cylinder head temperatures, which can lead to detonation, or preignition. Both damages a piston.