Yesterday while I was walking in the neighborhood with my dog, I spotted one of the first eco-cars I fell in love for. The Fiat Palio Weekend 6 marchas was available only in '99 and 2000, with a 61hp/60lb.ft. 1.0L engine backed by a 6-speed (6 marchas) manual transmission, while the previous base versions had a 75hp/90lb.ft. 1.5L and a 5-speed manual instead.
Altough at some point a significantly lower displacement won't actually help, the gears always play an important role for both performance and efficiency.