There is a 17 mile ea. way point A to point B then back to A, MUP route I ride fairly often. Today I was a good four minutes slower each way. There were two changes, first I lowered my air pressure, following the 45/55% based on my and the bikes combined weight. I was 80 psi. front vs. my usual 120, and 99 rear vs. my usual 120. The ride was definitely smoother, and didn't feel slower. The second change, I concentrated on spinning vs. mashing the gears. My knees felt much better, my heart rate was about 15 bpm average lower than usual.
Was the lower psi. more rolling resistance, the spinning a psychological thing, my legs were going faster, so I assumed I was going faster, maybe both?