I stopped at the autoparts store after work to take advantage of an oil change special on Mobil 1 EP and filter for the truck. They had just five quarts left of my desired grade. Two of the quarts where SN/DEXOS/GF-5 and three where SM... I asked they guy at the counter if he could check the back to see if they had anymore SN... He said what was out was the last of it and then asked me politely what the difference was. I explained and showed him the different seals etc... He seemed genuinely interested which was great because even I was taken aback by how nerdy I sounded. My fiance stood there, a look somewhere between bemusement and admiration on her face. I purchased the full five quarts and left. Funny how one website about something so innocuous to so many as motor oil can find an interest you didn't even know you had.