Changing oils is not very kind on the engine. The engine will be "confused" for about an hour. Some engines will hardly show it. some others will run worse during that period. It probably depends on the kind of oil change as well.
The same phenomenon has been noticed by investigated Blair and Jennings. Blair used radioactive tracers. When the last trace of radioactivity was gone, the engine ran better again. (Yamaha racing engines under test). It took about one hour for the last tracers to disappear, showing that all old oil had been replaced.
I too noticed a notable and quite temporary reduction in engine performance when I switched from a High detergent low SAE oil to a low-detergent high SAE oil.
In Bugman's report, I also noticed this behavior with some oil changes in the oils he tested.