I do not know what kind of car you have but most modern ones get their optimal fuel efficiency in the 70-75 MPH zone, and have for some time. The current class of 250-300HP engines will give you almost 30 MPG when cruising at 70 MPH, and about 25 MPG at 60 MPH. It is all in the gearing and torque bands.
yea and MOST cars fit that description....
I have noticed that as well. i keep track of my fuel economy and notice that when my cruise control is set between 70 and 75, I get at least 6MPG more than what my car is supposed to get on the highway. On the other hand , when I am on an FM road that is restricted to 55mph, my fuel economy is a bit below what I should get.
Modern hell? My 83 Cutlass has a '73 455 in it with an overdrive tranmsission and on the highway I get 26 mpg going 75-80mph.. It drops to 20-22 mpg in the 60-65 mph range. Of course I don't have steep rear gears (2.21 open rear).
My BS meter is pegged. Maybe it needs recalibration. I know someone's recently been pushing the idea that, for every 1 MPH over 55, it's like adding a nickel to the price of a gallon of gasoline (which is just a way of quantifying the point that fuel economy is worse). Obviously, that's intended to be a very rough average.
Seems to me that the optimal state for fuel economy is the slowest speed at which the engine is turning "relatively effortlessly" in the highest gear. I could be wrong but, it seems like for most modern cars, on flat terrain in no wind, that's between 40 and 50 MPH.
I think that's where my cars with trip computers show their highest fuel economy readings. At any rate, you've given me reason to check. And, I understand those trip computers don't really measure MPG. Mine have proved to be fairly close, though.
I drove from Mississippi to Wisconsin and back last week. We drive a Plymouth minivan with 3.3 liter V6. Most of the way the speed limit was 65 mph. For the most part, I kept the cruise set at 69. For one section coming home (about 200 miles) we ran 74-76 mph.
At the lower speed I got 22.3 mpg. At the higher speed I got 20.5 mpg.
Perhaps you are correct that the newer engines are configured to run at the higher speeds. Unfortunately, not all of us have the newer engines. With 125,000 miles on this engine, I probably would not run 80 mph across my beloved Texas. However, the fear of hurting my engine and not concerns about mileage or death rates is what would slow me down. There are places along the roads especially in West Texas where you can see from horizon to horizon and not encounter another soul on the highway. You are more likely to die from boredom than from a traffic accident.