Come across this yet, Vekke?
www.wardtro.de Andre´ Pötzsch Oldtimer- und Youngtimer Stellplatz Vermietung - vom 3l VW Lupo zum 2-Liter
To me, the most remarkable feat seems his leaving out 1 of the 3 cylinders, thus reducing displacement from 1.2 to 0.8 l ...
Sadly though, he doesn't back up his 2L claim with any factual consumption figures.