I will agree with most here that Mobil 1 is what I use as well. I will also add that since I've been having a long commute of 400-500 miles per week, I've been getting the higher interval stuff. I've been using the Mobil 1 15,000 mile oil along with a Bosch 15,000 mile oil filter in my Nissan SE-R for the last 6 years and it still runs like the day I bought it new. It has 150k on it.
For the Sonic, I have yet to change the oil but in a few weeks I'll be using the same Mobil 1 and since I couldn't find an extended life oil filter made by Bosch for the Sonic, I found an STP 10,000-mile cartridge oil filter. So I'll be changing the Sonic's oil every 10k instead of every 15k, until I can find a longer interval filter.
The way I see it doing it this way serves two benefits. It's actually cheaper to use Synthetic with a longer interval than conventional with a shorter interval, not to mention the time saved by changing the oil half or a third as many times. Also, I feel I'm being a bit greener than the average driver getting more use of the oil changes.