[Fat Charlie]

My morning run has plenty of rolling hills, but is overall almost 700 feet downhill. That means evening runs are almost 700 feet up so all else being equal, morning runs beat tank average nicely.

There's this one kid at work. I saw him coming up an on ramp in his big ol' SUV this morning and got ready to note mileage on my hand. He roared by me 2.1 miles later... because he's in a hurry to get to work. 2.5 miles after that I pulled into the parking lot at the same time as him and was opening up my area before he even got in the building.

Traffic and structural delays (lights, etc) generally won't let you sustain a higher speed. Since a higher top end isn't going to help you much if you can't sustain it, what matters is how much time you waste at the bottom end. If you don't screw around wasting time you don't "need" to do 80 when traffic won't let you sustain that speed long enough to help your time.