RedDog382

The fogging oil coats the internal surfaces of the engine ... valves, seats, combustion chambers, and rings. It helps prevent rust from moisture in the air and "sweating" that happen during temperature variations.

mjb

I have fogged my engines for years but never thru the fuel filter. I simply take of the air cleaner, rev the engine to about 2000 and spray the fogging oil into the throttle body until the engine starts bogging down, then I shut it off. I have never had any problems...at least none that I know of. Is this method adequate or am I doing harm to my engine??

Pismo10

There is concern of clogging up the sensors in the intake if you have EFI. Probably fine tho. Certainly fine with a carb.

bigboat28

When I fogged mine that way I could never get it to bog down, I ve even tried spraying 2 cans at the same time into the intake and it didn't bog. I too have been told that this messes up the O2 sensor. I think I might try the 2 cycle oil in the separator this weekend.

Pat McPherson

Mine didn't bog down with either method.
I think you mean the MAP sensor.
The 2 stroke oil in the filter was easier for me.

Boat Doctor

Mercruiser has a special way that they want all of the E.F.I. motors done. In a portable 6 gallon gas tank 64 oz of merc 2 stroke oil 12 oz of fuel conditioner concentrate and 12 oz of fogging oil mixed with 5 gallons of regular gas. Unplug fuel supply from the engine plug in 6 gallon tank and run engine @ 1200-1500 rps for 15 min. shut down and drain all water out of engine and block and all coolers. This will procetect all the fuel system componets(high pressure fuel pumps injectors and regulators) and the internal engine parts as well