What oil should I use?

I have a 1998 Chevy Malibu, v6. It has about 185,000 miles on it. The cap says to use 5w-30 oil, but the manual gives a chart that says if the temperature is above 0*F, I can use either that or 10w-30. I live in Georgia, and its about summertime... I don't foresee the temperature going anywhere near 0 between now and my next oil change. So, considering the temperature and mileage of my car, what oil do you suggest (grade and brand) that will keep my car running for a bit longer? I don't know the difference between one grade of oil and another, so help is appreciated.