I think Royal Purple is great if you're taking the Aveo to the track. Otherwise, it's overkill, especially if you've been using conventional all along. As the other commentators suggested, I would have her engine flushed, and then gradually wean the engine onto a synthetic. I would start using Mobil products. Start with using 3.5 quarts of Mobil conventional mixed with one of Mobil 1, change the oil every 4,000 miles, then at the next change, 2.5 qts conventional with 2 quarts of Mobil 1, and you get the idea. Despite what the naysayers may squawk about, the Mobil conventional and Mobil 1 synthetic will mix; they start out as the same molecular base as far as the additive and detergent packages are concerned. Once you reach using a full crankcase of Mobil 1, then bump the change interval up to 7,500 or 10,000 miles. If you're going to do the 10K interval, make sure you use ONLY Mobil 1 Extended Protection. Make sure you use only Mobil products, or if you must (clearing throat, Harrumph) Castrol GTX and Syntec. Don't mix the cheap supermarket or auto store stuff with the synthetic, or use a lesser synthetic (Quaker State, Pennzoil, Trash-o-la, etc.)