I used to do this all the time on my John Deere with the Kohler Command CV12.5 engine (12.5 HP). I had a sticky carb float and I hoped the lubricity of the MMO would help keep it unstuck. It didn't. Had to clean it out this year and that fixed it, I hope.
It didn't seem like it hurt or helped the power of the mower when I was using it. Did make the exhaust smell a little funny.
I'm trying a little bit of Lucas UCL in it now. It's hard to tell if its doing anything, as I recently replaced the entire fuel system from tank to carb. That made a HUGE difference. Seemed like I had twice the power after doing that (probably 'cause the old fuel line was all plugged and rotted out and the thing was starving for gas all the time).
later,
b