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.