Alvaro, I would like to have 66.6mpg as my worst tank. Last year I had to drive several highway trips for work and did worse than 55.5 (4.2L/100)
1st Spring tank : 1119.1mi @ 69.35mpg - 1800.7km @ 3.392L/100.
Sadly lower than the previous 70.18mpg - 3.352L/100
Considering the 2 hours of stop&go traffic during last 2 weeks, which should be at least 1.2L (0.32gal) wasted, it would have been 70.73mpg.
At least I found that my 60L (15.85gal) tank contains at least 61.08L (16.14gal)...
I have 2 tanks (I may not have sufficient mileage before end of June as in May I will have to work during 3 weeks in Paris) to beat my 1902.1km - 1182.2mi tank.
Have fun,
Denis.