That's the muffler.

You didn't by chance pour the gas into the oil fill tube did you?

Ha really? I agree with bill.. Fuel in the oil it seems 2 me like alot of people are doing that here lately. One of my neighbors just did that to a brand new honda mower.

Do you happen to own a gas weed eater

'Do you happen to own a gas weed eater'

Not a bad idea, but in fact using 2-cycle mix in a 4-cycle rarely produces exhaust smoke. If you gassed the oil, obviously dump it and change it. Most likely the only effect will be a really clean engine on the inside. In this case, you would also check the paper air filter for oil contamination and replace it if it looks oily.

You could also just buy a new one if you want. Maybe it's a sign?

Here is a link that might be useful: O'Connors Lawn & Garden

Saxman, I'm not doubting you, I'm just curious.
How does oil in the fuel contaminate the carburator
air filter?

Through the breather. The rubber pipe going to the intake. The gas added to the sump raised the level so it was getting sucked into the carb. This same scenario occurs from a stuck needle valve too.