The factory oil (that came in your Stinger) is Total Quartz 9000 Energy HKS G310.
For some reason, I'm having serious issues posting. It keeps saying it looks like spam. I'll try removing all useful information and see if it works. You can PM me for a link to the source of that information, because the site won't seem to let me post it.
HKS G310 is an extended mileage oil, designed to last 30,000KM or 18,641 miles. The standard 9000 series can be ordered on Amazon for $38. I did a lot of research, and Total oil actually is better than pretty much anything else. It's the manufacturer recommended product for all new German makers as well as Hyundai/Kia. Using Mobil 1 probably wouldn't make much of a difference, but you should get slightly better mileage and longer engine life with Total.
I wrote a fair amount about oil, which rating to use under different conditions and why, but I am guessing the few paragraphs of info was the issue with posting? I don't know. Anyway...
In short, if you're trying to decide which oil to buy, Kia's answer is Total Quartz 9000 5w-30.*
*which rating depends on climate, and whether you have a 2.0L or V6. I've deleted all the explanations on which to use and when. Hopefully this will go through.