Back in the day, it was the essential gasoline performance additive. But it turned out to be incompatible with catalytic converters and (to some extent) human brain development. Well you can't have it all.
Anyway, the only reason this might be of interest to the hypermilers at CleanMPG is I stumbled upon a web site with vintage ads (from National Geographic!) extolling the virtues. The one I link below seems to have some real significance to the sport. Take a peak and see it you agree:
I really think the top half could be a fine home page for this web site - just one reporter's opinion.