2014 Ford Fusion SE. Better fuel economy than advertised?

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Hey guys, I have a 2014 Ford Fusion SE with the 2.5L I4 duratec engine. I purchased it used at 70k km and it was mostly used for highway driving before I took ownership. Now when I first drove it I was stunned at the fuel economy difference since I was coming from an SUV and it hovered around 9.5. Now I have recently crossed 100k km and did an oil change recently using Quaker State 5W-20 "high mileage" oil and after doing so, resetting everything and driving around the past few days; I've noticed that not only is the engine smoother with less vibration through the chassis, but my fuel economy hovers around 8.4 max thus far. I thought the ecoboost engines were supposed to be better than the 2.5? I'm very happy with the car either way as it's always worked great mechanically and $20 CAD gives me nearly a half tank of gas, which lasts me usually about 3 weeks.