In most cases if you are using an oil of the same weight and specification, then a majority of what you hear is just placebo. If anything, you may have improved the flow of oil by changing to a new filter, but in terms of the oil itself, it's mostly an illusion. Your mind is really good at doing things like that to you. Well considering my last service was at the dealer so I would have no clue what they use but I doubt it was a 5-40 semi syn like I used. I hope it's not placebo because overall the car just sounds and feels like it is running so much better. I don't think I'll ever be taking my car to a dealer ever again because I couldn't even get the cap off. Chances are since it doesn't come off, no one has bothered to remove it and left it as is. A-holes. For it to get that tight would be that they didn't use the filter wrench to re-tighten the housing but a **** socket wrench and tightened from the cap. Not being able to get the cap off made for a very messy oil filter change.