Well, this explains a lot. I have been driving a 5-speed and have been
getting awful mpg in city. Now I am realizing I am shifting at very
high rpms, around 2500. I will try to lower the rpms during shifting
and see if it makes any difference.

(I think one problem in my particular situation is that the type of
engine I have derives it's power from high rpms, you have to rev it to
get going, and I don't like it)