The
Citroën 2CV was designed just before World War II and was hypermiled at
over 63mpg once (50mpg not uncommon). Of course, an engine size of 375-600cc is not exactly powerful, but it was very durable and was built from 1949-1990. Interestingly, the original was aluminum and had rear wheel covers like the Insight.
Variations were made:
While very few would settle for such low power today, it contrasts with the amount of power many people think they need today. Causes me to think a small 100mpg sedan is within reach if the public could tolerate a 0-60mph acceleration in 15 or 20 seconds.