changing the oil in a mower at all is a good idea, the supertech stuff is alot better than no oil changes at all.
With our lawn equipment I change it twice a year. Before I put the lawn equipment in the garage for the winter, I change it with some diesel oil, whatever I have on hand. Also when I winterize the lawn equipment, I pour some stabil gas treatment in with a full tank of 87 unleaded.
Then when the spring mowing season comes along, I change it to some 30w castrol or whatever decent brand I see.
I change the three dollar air filter and the 89 cent spark plug once a year.
With maintenance like this the motor will outlast the rest of the mower thats for sure.