Where do you stays? Your first picture translated to about one hour to cover 50km. This is the very ideal case even my turbocharged car can do 20km/l. Most cars do very good at this pace.

You are so lucky. Most of us in the city jam always and we typically take 1.5x longer time to cover same distance as you. In between includes 100km/h+ and also 15min crawling to cross one traffic light.

Can you get 13km/l on a bad day when it takes you 80 min to cover the same distance as your first pic?

Showing the average speed is the better indicator.

The so called city driving that most put remark doesn't include traffic condition, no rush hour city driving in 50-60km/h range is more economical than speeding in highway.
Highway driving also if KL area, within the metropolitan doing mostly 80km/h range also far cry from speeding at NSE.

Here's spreadsheet I developed to compare transmission of various car type at redline and 3000rpm. It shows their theoretical top speed if not limited by engine power or electronic.

More powerful engine can afford to have wider overdrive gear ratio thus cruise at lower rpm, it is the transmission.

Gearbox change speed and torque. A 10 to 1 (10:1) speed reduction gear set reduce the speed from driver to driven gear by 10x, it also amplify the torque by 10x. In overdrive, it is the other way round 1:2 ratio double the output speed, but drop the torque by half.

Not related with automotive, just car enthusiast. But my work is need linear algebra and calculus, so this spreadsheet is relatively quite simple

That one covered in high school physics, and kemahiran hidup, maybe back in my old days.

lol, I'm lazy. I give you the formula you make one want or not?