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I got a loan of my son's mower and looked at the oil. It looked and smelled smokey. I changed the air filter, cleaned and gapped the plug. Then, I changed the oil twice after just one hour of use each time and the oil is still smokey. The mower starts easy and runs well. It does not appear to use oil or have smoke in the exhaust. WHAT GIVES?

so the oil is a grey color? water may have gotten into the crankcase, or the float needle on the carb is bad and allowing fuel to flow into the crankcase past the piston when it's off..
does the oil smell like gasoline?

To answer you response: the color is very dark, perhaps black. The color seems to be a colleterial solid in nature or perhaps soot like. Smells like exhaust.

Again, mower starts easy and runs smooth. No oil use. No exhaust smoke. The mower originally did require two or three pulls to start before I added a new air filter and a clean plug. But ...

The son apparently tipped the mower on the air filter side, as the filter looked oily and dusty. Oil on the air filter - over fill of the crank case or a tip over?

He must have run it with a partly plugged air filter for some time. Is it also possible the engine internals to be very coked up from a rich mixture? I added a fare amount of Sea Foam product to the fuel, but this treatment may take time to work itself through.

Is it even possible for products of combustion to blow downward through the cylinder rings into the oil? Everyone knows about the opposite, of oil coming up and being burn in the cylinder and making colored exhaust smoke which is not the case.

SailDriver said:

Again, mower starts easy and runs smooth. No oil use. No exhaust smoke. The mower originally did require two or three pulls to start before I added a new air filter and a clean plug. But ...

The son apparently tipped the mower on the air filter side, as the filter looked oily and dusty. Oil on the air filter - over fill of the crank case or a tip over?

He must have run it with a partly plugged air filter for some time. Is it also possible the engine internals to be very coked up from a rich mixture? I added a fare amount of Sea Foam product to the fuel, but this treatment may take time to work itself through.

Is it even possible for products of combustion to blow downward through the cylinder rings into the oil? Everyone knows about the opposite, of oil coming up and being burn in the cylinder and making colored exhaust smoke which is not the case.

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It's called blow-by caused by worn piston rings. The oil on the filter might be caused from the blow-by gases exiting the breather hose behind the filter. By the sounds of it I wouldn't spend too much time and money on it.

The forum is not an Agatha Christie book so there is no point in hiding vital clues till the last chapter.
Tipping the mower carburettor side down allows the sump oil to get into the carb , air cleaner and manifold.
Once you clean enough oil out it is just a matter of time to burn it all off.

If a shaved gorilla pulled the start rope hard enough & there was more oil in the cylinder than the volume of the squish ( TDC ) they you can do things lke blow kead gaskets , break piston rings or even bend con rods .
However in most cases the oil will simply burn off over time which can be a few hours.
Carbon fouling of the spark plug can happen so you might need a new one if the engine becomes really hard to start after a few uses .

If the oil is not changed regularly it becomes extremely black. U can change it and when the new oil coats the inside of the engine and washes the old black oil off the inside of the engine it will mix with the new oil and turn the new oil black.

bertsmobile1 said:

The forum is not an Agatha Christie book so there is no point in hiding vital clues till the last chapter.
Tipping the mower carburettor side down allows the sump oil to get into the carb , air cleaner and manifold.
Once you clean enough oil out it is just a matter of time to burn it all off.

If a shaved gorilla pulled the start rope hard enough & there was more oil in the cylinder than the volume of the squish ( TDC ) they you can do things lke blow kead gaskets , break piston rings or even bend con rods .
However in most cases the oil will simply burn off over time which can be a few hours.
Carbon fouling of the spark plug can happen so you might need a new one if the engine becomes really hard to start after a few uses .

Click to expand...

Would the gorilla absolutely have to be shaved?