Fuel per km

[Eric.B]

Most military contracts in the year 1900'ish asks for a pickup with a fuel consumption-level at 6 km/l. You should build such an engine while still having up towards 45 hp and being less than say 3500 cc and that isn't that difficult. But then you put the engine into a vehicle the fuel consumption jumps.

A engine which would go 6 km/l (I think the highest I got is 11 km/l) is suddenly down below the required 6 km/l.

Vehicle contracts require the vehicle's fuel consumption rating. Do not look at the engine's fuel rating because it is not the vehicle's fuel consumption, it's the engine's.

Is this due to the fuel consumption being recalculated when you're building a vehicle? If so then it means that I have to focus more on light weight pickups, and fuel efficient engines/gearboxes.

That is correct. Vehicles take into account, aerodynamic drag, rolling resistance and gearing. The fuel consumption listed for the engines is what is called Brake Specific Fuel Consumption. As in the amount of fuel it uses when it's not attached to anything.

To give you a real world example, Honda makes a 1.5L engine. Alone it uses about 300grams per kWh, estimated at around 45mpg. Inside a Honda Civic it does 40mpg. Now imagine putting it inside a Panzor Tank. If it's even able to move it, it'll be using a lot of fuel, probably 5-10mpg...