Originally Posted by echo7tango
On a recent trip, flat highways, 60 degree temps and little wind, I got:
25 MPG at a steady-state 85 MPH
28 MPG at a steady-state 75 MPH
34 MPG at a steady-state 65 MPH
45 MPG at a steady-state 55 MPH
These MPG values were as shown on the EVIC's instantaneous MPG values when driving for a few miles. Elevation was near sea level, between 200 and 600 feet.
I duplicated my 45 MPG value the other day, on Friday 13 March, from Mountain View, CA to Hollister Hills SVRA and back. This was on highways CA-85 and US-101 at near sea level (elevations 100' - 300'), gently rolling hills, no appreciable wind (trees, leaves and grasses not visibly blowing), and with the A/C on.
On the freeways at a cruise-controlled 55 MPH for the 98 miles there and back I got 45.3 MPG. That's basically 45 MPG for 100 miles!
I did this by:
(1) getting up to cruising speed on the freeway;
(2) then, setting the cruise control to 55 MPH;
(3) then, resetting my EVIC trip odometer.
I read the EVIC's reported trip MPG before I slowed down to exit the freeway. My JGC is stock, no roof rack (yet), with Goodyear Forteras inflated to 38 psi.
At 55 MPH everyone is passing me. Big rigs driving near their legal speed (55 MPH) were also passing me. Of course I stayed in the far right lane except a few times when traffic was merging at an on ramp, and only if the left lane was clear I merged over for a few seconds and then merged back. Most of the time, though, traffic to my left lanes were going 10-20 MPH faster than me, and I just stayed right.
In 3 weeks I drive to LA, then Phoenix, then Las Vegas by way of the Grand Canyon's South and North Rims (hopefully the North Rim isn't snowed in). On that road trip I plan to make more measurements and report. But, I don't like driving slowly!
Here's my planned 2,200-mile route: https://goo.gl/maps/o3Cle