Optimal rpm for fuel econmy???

[Beatty, Robert]

Gang,

Been wondering for the past month while watching how my milage varies
depending on how fast I drive to work, how is the optimal rpm figured for a
car?

I know in boats and in planes a top speed is known and a cruising speed is
also known.  How about in a car?  Now in the 70's, 55 mph was pushed as the
most economical speed and it was the national speed limit as well here 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?

Now that I'm sure I have started a thread that will last for a while, I'd
better ask my other question.  That being, if one can change the optimal rpm
for economy in a car, how can I do it for my 86 5ktq?  Since I usually drive
at about 68-72 mph to work, if I could get the same milage I would get at
55mph, I could save buttloads of $$$ at the pump and save myself time as
well :).

Let the arguing commence :)

Rob Beatty
86 5ktq
89 200tqa