I'd agree that it probably would do better with an Xw40.
I'm not a particular fan of Pennzoil's SRT 0w40 compared to, eg. M1 0w40. Of course its hard to tell from cheap lab analyses, but it *looks* like its nothing more than a heavier version of their ordinary Xw30 oils, without the bump up in additives that you normally see in performance 40-weights. It is, after all, tailored for engines that are all roller-cammed, contain no gear drives, etc. The SRT engines (now that the turbo 4-cylinder isn't produced) are all very easy on oil and don't demand anything "special" in stock form- and that's what the SRT 0w40 is made for. However, the analyses of their "Euro" 5w40 looks more like a performance-engine oriented oil akin to M1 0w40 or Castrol 0w40. I think that's what I'd go with if I were sticking with the SOPUS product line. That or RT6.