What are the current speeds for peak fuel efficiency as set by auto makers?

Question

The last time I bought a new car (when Clinton was getting a winski in the oval office while on the phone with Senators) the peak fuel efficiency for a car was at 37mph city and 55mph highways. Has that changed?

I currently I drive a 2004 Freestar, which I bought from Enterprise Rental, for use as a taxi cab. In the last six months, my fuel costs have risen $100 a week, equal to nearly 20 hours of net income, when you divide the total number of hours I operate by the how much money (including tips) I have left after expenses each week. Unless there is a valid reason to hurry, I'm doing 55 in the 65mph zones on the freeway. I'm getting to know the right hand lanes real well.

Answer 1

car manufacturers don't "set" a peak fuel efficiency speed.   but, yes the peak efficiency speed is about 50 to 55mph

Answer 2

from what i have heard, peak fuel efficiency is at 70-75 mph. ,i do not remember where i heard that, it was too long ago.

Answer 3

Of course, but they were set by the goverment, not auto makers. The whole reason behind the 55 mph is for fuel efficiency. Drive the speed limit and save gas!

Answer 4

I've wondered this too. CAFE (corporate average fuel economy) standards were set up in the 1970's when the speed limit was 55mph, so are standards set at a higher speed now? If you are asking about peak efficiency for specific vehicles, they are all different. Generally, peak efficiency comes slightly above the speed when the car is first able to drive in top gear without lugging. Some cars lug at 1500rpm and others at 2000rpm.

Answer 5

According to this site, MuzzleYourGuzzle, the peak efficiency can best be achieved around 60 mph.  This goes along with the theory of having it "slightly faster" than the standard speed limit of 55mph.  (but now with limits set at 65mph in most states, maybe this has been updated.)

Answer 6

Most Inerstates have a minumum speed limit of 55...