Accidentally Mixed Up Motor Oil Grades - Next Step?

What is your question?

I accidentally added a half quart of different grade of motor than what was in the engine by the same manufacturer Mobil 1. The car seem to run okay, but do I need to change the oil as soon as I can or it will not matter. My car manufacturer recommends 5-20 weight and I put in a 5-30 to top off. Thanks,