Optimum Highway Speed

I consider the source. If the charts are from Wayne, then IMO, they are accurate. He lives for this kind of stuff and takes it seriously. He won't be configuring charts while going downhill, with a strong tailwind, tailgating an 18 wheeler, etc...

 

Bob Wilson has posted a lot of good information on Priuschat from experiments he has done. You should review those:

Such as:
Updated MPG vs MPH chart | PriusChat

kevin

 

There is a trade off, optimum speed for mpg vs value of your time, to me cruising at 55 on the highway would be a waste of my time.

 

True and this will be a different value for different people, worth noting it is average speed that counts for journey time.

 

According to Graphics of average fuel economy vs speed | PriusChat for the gen 3 there is a sweet spot at 38 and maybe 61 mph?

 

The horizontal values are in kilometers per hour, and the vertical values are liters per 100 km's. With the latter lower values are better.

 

I just can't agree to his data collection method. It scrambles and mixes in far too much other activity. The included accelerations and decelerations render it almost meaningless for this purpose.

The sweet spots you think you see, didn't appear in the the steady speed mpg vs mph tests run by Wayne Gerdes on CleanMPG.com, or on similar tests by a member here (unfortunately, the primary chart image was lost in a website host migration, but copies still appear elsewhere):
Updated MPG vs MPH chart | PriusChat

 

I probably write the same thing over and over again, and boring ..... but what looks like optimal in one direction of a trip can be way off in the other direction of the return trip using the same route in both directions. So much depends on all the conditions of each route driven.

 

I'm also interested in that dip around 100 km/hr...FWIW

 

There are other dips besides the dip at 100 kmh they are just not as noticable. If you get an accurate estimation of that dip at 100 kmh than you track at 60 kmh enough to see that difference, than move onto 130 kmh you'll see just how much of a dip the car will show you per speed and other conditions.

When it starts getting really cold most of us play a lot less attention to how much gas the Prius uses.