As I tried to say, the 1.6D - and the French car using the same engine as well - have smooth power from idle that's the same in all gears. My engine simply do not deliver the same power under any conditions that it does in 2nd to 6th.
Over at
www.spritmonitor.de there are lots of enties from various drivers of all sorts of brands, and there is little to support the idea that modern cars drop noticeably the amount of fuel they use with mileage, if at all. The lowest entrance from the first tank listed is a V50 DRIVe that delivered 92.6 mpg - from new. But again, consumption worsen on mine instead of improving.