More power and soo much smoother after oil change?

[ohhh my]

I purchased my boxster from the previous owner who took meticulous care of the car. Before he sold me the car, he changed the oil and used Mobil 1 0w40 and told me I didn't need to change the oil, so I didn't. (I know most of us change the oil as soon as we purchase a car)

Works been super busy and I didn't haven't had a chance to change the oil until today after 7,000 miles, when my initial plan was to change it at 5,000 miles. The oil was pretty dark as expected.

But after my oil change, it seems my engine is soo much smoother and has more power. Is this normal and expected?

Wow!