Very strange. If you go to Pennzoil main website and choose oil selector. 2015 & 2016 Chevrolet Silverado and the 5.3 engine are not given as an option anymore. The GMC Sierra is, but when you select to, it tells you to call pennzoil...it won't make a recommendation. Is this just a glitch or is this something to do with new formulations and new Dexos?