I have about 16 qts of this oil (bought when Autozone had their clearance) waiting it's turn for my Golf 2.5L. Maybe 2 yrs in the future till my Pennzoil Euro 5w-40 runs out. Out of curiosity I bought some Pennzoil Euro 5w-30 @ Walmart for $22 5 qt. jug. I wanted to do a "winter" blend so I mixed 50/50 of the 5w-40/5w-30 oil. My 2.5L engine runs smoother and revs quicker w/this thinner oil. (I could immediately see how much thinner the 5w-30 oil was compared to the 5w-40. Also, the thinner oil was much lighter colour in appearance.) I'm thinking I'll not be going to using straight 5w-40 any longer. My point...maybe try a Euro 5w-30 oil (or a blend) and see if your engine runs better. Between my new NGK Iridium spark plugs and this oil, the Golf is driving so, so nicely.
2012 VW Golf 2.5L Auto Pennzoil Euro 5w-40
2005 Ford ZX5 2.0L Auto
1999 Mazda Protege 1.6L Auto