CHANGES in efficiency at speed relative to ICEs

[AudubonB]

I came across a comment in Ohmman's "Favorite/Least Favorite" thread regarding energy inefficiency, thus:

Least: Inefficient power consumption. Currently on a road trip through Montana and went over 600 wh/ml at high speeds / elevations through stretches. Wind drag and weight make it feel heavy when compared with the S.

and it made me wonder whether this possibly could be some inherent defect of either the Model X or EVs in general.

I do NOT think this is the case; rather, those of us driving Teslas have become acutely aware of our vehicles' energy consumption because the data displays are so much further advanced than in any ICE. The best that I know of in a traditional vehicle is "Instantaneous mpg" (terribly misleading and inaccurate enough to be fundamentally worthless), and "mpg since latest re-set" or some such.

However, in that I am accustomed to hauling heavy loads many thousands of miles at a time over wretched roads, I can attest to the reality that my diesel F-350, in which when empty and on good roads I can attain 18mpg driving reasonably (60mph) and 22mpg driving parsimoniously (50mph), sucks up the fuel at 8-9mpg when driving 65mph, loaded, and on poor, hilly, and snowy roads.

So there I have one fairly floppy datum of a difference in energy consumption of close to 3X. As usual, I'm presenting what is probably an outlier, but I think it could be valuable to have some more rigorous data concerning how fuel economy changes in ICEs as driving conditions change to less than ideal. Has anyone such material?

 

[Saghost]

It's such a complicated subject that I don't really think you'll find much good universal information about changes.

You have to look at both the changes in loads (it takes more energy to move a car faster, or a heavier car, or a car in colder weather,) and to the engine/transmission operating point (internal combustion engines are usually most efficient at wide open throttle at just under the torque peak rpm, and may use twice as much fuel to generate the same amount of power at different operating points.)

 

[vandacca]

The problem is that most ICE drivers don't care much about fuel economy since they can stop just about anywhere to refuel. Although, that may change when gas is over $5/gallon.
At the moment, EV drivers need to pay special attention because "recharging" is much more limited.

 

[AudubonB]

That's a bit of a blanket statement that does, however, contain a kernel of truth. My situation is one where fuel economy most definitely does matter, as throughout the North Country not only are there supremely long distances between re-fueling stations, but the most propitiously located ones charge an enormous surcharge - 100% over the "prevailing" price is not uncommon - to take advantage of their situation.

Regardless, you are correct in asserting that EV drivers as a group need be more attentive to their consumption than do ICE drivers.