New tires = 20% efficiency loss?!?!

At 83k, it was finally time to ditch the OEM tires. Getting that many miles out of original tires is proof I drive quite gently (most of the time, anyway)

Yesterday I bought a set of Bridgestone Turanza QuietTracks.

And quiet they are, but I sure seem to have taken a heckuva efficiency hit. My lifetime dashboard efficiency average is 4.81 mi / kWh since most of my driving is in warm flat Florida at around-town speeds - more evidence of my conservative driving style.

Yesterday's driving characteristics (even less freeway than usual) should have resulted in a daily calculated efficiency in the 5.0 - 5.25 range, but all I got was 4.21.
Midday, I aired them up to sidewall max (50 psig) - that seemed to help, but not much

Yikes - I sure hope these tires get better with age!