I have a new Toro lawn mower, Briggs & Stratton engine. Model 20053.
I've been using it since the last week of May.
I mow about 6-8 lawns per week, and last week I noticed that the mower
would let out a think white smoke when I start it, since then I only
prime the mower twice instead of thrice. Now, yesterday I decided to
clean my whole mower, and found that there was gas and/or oil on the
air filter. Now you're probably thinking, that leaned it over on the
air filter side, but I assure you that everytime I've leaned to mower
over, the air filter side was up. So I use a paper towel and squeeze
the oil/gas out of the Styrofoam around the filter. I dry the case,
which is also oily. I mow my lawn, and afterwards I see that there is
new oil around the case, and on the filter.

I figured maybe I have too much oil, so I checked it about 10 times,
and it seems fine, I didn't even put much oil in the machine, it says
it can take 591ml and I put about 500 and it was at the full line.

Any help?
Thanks.
Mitch