Do both — but the carburetor gets the important shot

Spraying into the cylinder alone isn’t enough. The correct method is to spray into the carburetor throat while the engine is running, then kill it with a final spray, and yes, you can add a direct cylinder shot afterward if you want to be thorough.

Here’s why the carb spray matters: when the engine is running and you spray fogging oil into the throat, the engine sucks that oil through the intake tract, past the valves, and into the cylinders. That coats the valve stems and, more importantly, the valve seats — which are the first things to rust on a stored engine. A direct cylinder spray only protects the cylinder walls and rings. The valves sit dry and unprotected all winter.

If you only do one, do the carburetor while running. But the best practice is both: fog through the carb until the engine starts smoking and stalls, then pull the spark plugs, give each cylinder a 2–3 second shot, and crank the engine a few times to spread it. Takes an extra two minutes.

One warning: don’t spray into a cold, non-running carb and expect it to work. It just puddles and never reaches the cylinder.

Ten extra seconds now beats a valve job in spring.