I don't run with power yet but I just did a similar test. I will put as much information that I have here. The past 3 Sunday's I have ridden the same route. 15 miles with elevation gain 535 feet, elevation loss 554 feet. 100 psi. Garmin 920xt.

First ride was stock aluminum wheels (Specialized DT Axis 2.0) with stock tires (Specialized Turbo Elite)
0630am, 65°, average mph 19.7, max mph 30.6
5 miles 20.0 mph, 15:02 min.
5 miles 20.4, 14:43
5 miles 19.0, 15:48

Second ride was Reynolds Aero wheels 72mm with same stock tires;
0630am, 55°, average mph 20.1, max mph 32.3
5 miles 19.0 mph, 15:47 min.
5 miles 21.0, 14:17
5 miles 20.5, 14:38

Third ride was Reynolds Aero wheels 72mm with Continental GP4000 ii;
0630am, 65°, average mph 21.2, max mph 35
5 miles 21.1 mph, 14:12 min.
5 miles 21.2, 14:08
5 miles 21.5, 13:58

On the second ride I did go out a little easy on the first 5 miles because I have never ridden deep wheels and I had already blew out a tube (pinched and scared the shit out of me).

Edited to add times to 5 mile intervals.

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