My parents now live in NC, and one of the highways on the trip there has a posted speed of 80mph. Back when I still had the Prius I got 38mpg doing 90 on that road.

I had to make a run from Tiverton out to Cranston RI on I195 this past Sunday with a tail wind and light rain I got off at Cranston Street from 10 south and had 48.4mpg for the trip mostly following a Prius at 55mph. Then had to turn around and go back and on the return trip I was doing 70mph on a slight up hill into heavier rain and a head wind and was gettting 32mpg instant at a steady speed. I still managed to pull 43.9mpg for 136 miles for the day.
There was a graph I saw years ago I think someone posted it here with the mpg vs speed for a Prius - it does drop pretty quick as speed increases. The new model has a real straight down air dam front end compared to the older models - major different look.

if you get in the high speed lane and go 70 you will increase peoples FE by 2-7 mpg that drive behind yo,u so by 20 cars driving 70 and not 80 you are saving potentially 140mpg for the fleet of 20 or so cars, pretty impressive.

On a related note, a attentive driver in stop-and-go traffic can actually reduce or even eliminate traffic waves behind.

Very fascinating series of articles here:
https://amasci.com/amateur/traffic/traffic1.html

I drive a 2002 Civic Si. When I drive like a total idiot, in the freezing cold, I get around 28 mpg on the highway. But yea, I see your point.....
:D

I am always trying to smooth out the jam waves by looking as far ahead as I can and maintaining a constant speed. I get so pissed off though when I get behind a large vehicle that blocks my view and the driver is obviously clueless to the concept by propagating it further despite their superior view of the road ahead. All you can do is just try to average it out without being a roadblock. :p

I've found that my Si seems to do almost as well when it is driven aggressively as it does when it is babied. I'm stumped.

On my drive to work (18 miles), I drove hard for one tank, then easy the next. I repeated this three times. My mileage for all tanks was within one mpg of each other.

How cold is it where you are when you are getting 28 mpg highway? How long does it take for your car to warm up? Mine was still switching back and forth between open and closed loop until I had run it 20+ minutes this morning (14 degrees outside). I logged 29.9 mpg on the way to work.

I had a full sized van for travelling (and sleeping in to save $$). One night on a freeway in california, I was keeping a constant speed, while traffic did the accordian thing. The guy behind me went crazy - literally. He gave me the bird, starting with one, progressing to both, out the sunroof, eventually honking, and flashing his lights, and swerving. The whole time, he could easily see that no one was going anywhere. He would try to swerve around me, but there were people there. Eventually, he managed to cut someone off, and tried to cut me off, but the accordian in front of him condensed, and instead of stopping, he proceeded with his plan, and slammed into the side of my van, totalling his new Trans-Am. His wife woke up in the passenger's seat as I called the police. He was taken to jail, and I went my way. There was a slight crease in the body of the van under the sliding door, that didn't affect anything.
I would do it the same way again, as I have for over 15 years, now.
The same van was rear ended by a teen, doing the same type of driving (not irate, though). Another scratch, and another totalled car.

I tend to agree with that statement because that is almost exactly how I get the best gas mileage on the highway. Its better than to set cruise at 5 over and get stuck behind a guy going the speedlimit in traffic. Well, that didnt really make much sense, but i dont really know.

Bah, I just confused myself, but still agree with your statement

Thats funny, I actually had close to the same thing happen to me on the beltloop, but with two exceptions, I was the teen, cut this one mexican off because he pissed me off by cutting me off first, so he decides to take a full size SUV into the 6 foot space infront of me. I was the last car in the accordion at the time, so I slammed on the breaks so hard the ABS kicked in. I DID NOT want the front of my car to be smashed by an explorer, and I didnt want my (at that time) week old car totaled.