V2.5.0.2 Strangely fuel-efficient competitor vehicle

[AstraMeccanica]

It's 1905, and the best phaeton on the market — the Heilen by Eisenwerk — is remarkably fuel-efficient.

To give an idea, I’m attaching an image comparing it to the second-best phaeton of the time (based on type rating).
Is it normal — or even realistic — for a car to be this fuel-efficient in 1905? And more importantly: how is it achieving this? It appears to use a 4-cylinder engine, which makes the result even more surprising.
The only explanation I can think of — though it seems impossible — is that it somehow benefits from 1930s-level aerodynamics.

But here’s where things get even stranger.
To assist with vehicle design, I’ve linked Power BI to the save database to analyze how competing cars are built.
Assuming my formulas are correct, the Heilen as a whole averages 19 km/L despite running on an engine that gets 13 km/L.

I’m not sure if this is a bug or not. If it isn’t, I’d like to understand how I can achieve this level of efficiency too.

I'm attaching save and image

[Eric.B]

But here’s where things get even stranger.
To assist with vehicle design, I’ve linked Power BI to the save database to analyze how competing cars are built.
Assuming my formulas are correct, the Heilen as a whole averages 19 km/L despite running on an engine that gets 13 km/L.

This has been the case for many many years. The game lets you gear a vehicle to improve fuel economy greater than the engine's rated fuel economy. It's capped at a maximum rate a certain percentage above the engine's rated fuel economy. (Similar to how if your engine is too weak, you get a minimum of around half of the engine's rated fuel economy.) In other words, this vehicle is strong enough to drive normally at pretty much idle.

Also, this design does not suffer any vehicle weight penalties because it's large enough to move the vehicle. Thus allowing for better fuel economy.

The Oldsmobile curved dash got around 30MPG. The game's vehicle is rated at 44MPG. The Maxwell Runabout was a 4-cylinder and got upper mid 20s.

So, it's not too far off from realistic, though remember, a lot of things have changed to sub-components ratings, skills, and their effects. I see that you attached a save game, thank you. I will add it to the balancing pool. Be sure to keep playing through and include your saves when you get into the later years. I won't be working on GC again for several months, so I will take a look at it then.