[HypermilerAX]

I corrected the volume of the first test. I took 1,00 L for the first bottle I put but the station volume is not as accurate (only 10 mL) as weighing.

Recap :

Before :
Temperature : 25,7°C
Pressure : 1021,1 hPa
Humidity : 43%
Air density : 1,197
Wind speed : 13 km/h NNW
Sunny
Engine at operating temp
Tire pressure raised to 2,8 bar

Fuel consumed : 840 g = 1015,7 mL (827 g/L at 25°C)
Distance driven without EOC : 28,56 km
Consumption : 3,556 l/100 km
Recorded average speed : 80,26 km/h

Corrected consumption (80 km/h and air density 1,2) : 3,547 l/100 km

After :
Temperature : 20°C
Pressure : 1020 hPa
Humidity : 77%
Air density : 1,220
Wind speed : 12 km/h NNW
Clouds but dry road
Engine at operating temp
Tire pressure raised to 2,8 bar

Fuel consumed : 748 g = 901,2 mL (830 g/L at 20°C)
Distance driven without EOC : 27,30 km
Consumption : 3,301 l/100 km
Recorded average speed : 80,23 km/h

Corrected consumption (80 km/h and air density 1,2) : 3,255 l/100 km

Before : 66.16 mpg
After : 72.28 mpg

This is exactly what I expected. It's an 8.2% improvement for a 15.1% higher ratio (MPG gain = 55% of ratio change).