I was at my local Walmart today and noticed that for the 5w30 grade of Royal Purple, there are 2 different looking bottles. The first batch, which looked like it had been on the shelf for a longer period of time, had the "5w30" in black lettering, had "SL" in bold on several places on the back of the bottle, and had different "descriptors" for the oil on the front of the bottle than the newer looking ones, which had the "5w30" in purple lettering, and no bold letters on the back of the bottle. Did RP just change their bottles up a bit? Did their oil formulation change? The part numbers were the same on both bottles. I'm just curious.