5W-30 oil wouldn't have done any damage. But you DO want to run the SAE30.
When you changed the oil did you have the mower turned on it's side? When the engine is tipped to the side oil gets into the cylinder and usually ends up in the muffler. Replace the spark plug. It's probabaly oil fouled. Then start it up and let it smoke. It will burn the oil out of the muffler in a few minutes then it will stop smoking.
Rick
May 2006
howtomendit.com for free repair help, information and advice.
