Optimal rpm for fuel econmy???

[nicksimc]

>also known.  How about in a car?  Now in the 70's, 55 mph...as the
>most economical speed and it was the national speed limit...in
>the US.  Was 55 just pulled out of the air for a top speed requirement or 
is
>it actually the most economical rpm/speed for a car?  And if it is,
> shouldnt
>various engine sizes and types allow for other speeds to be the most
>economical?

It seems most 'commuter' cars, have been engineered/factory tuned to
run most efficiently at highway speeds, even before factoring in the
start-stops of city driving.   When the national speed limit was repealed,
Mercedes-Benz dealerships offered the option of 'adjusting' older
Mercedes so that they would run with greater economy at the higher
speeds now allowed.  I'm not sure exactly what they were adjusting, but I
know it wasn't free. :)

M Nicksic

82 4ks -25 mpg @ 70 mph hwy between 2k-3k in 5th
84 4ksq - infinite mpg @ 0mph garage (until sorted out)