My carbed 45 did 5,5 l/100 km on a freeway yesterday, constant speed 130 km/h, I was the only person in the car.
When fully loaded, it does 6,25 l/100 km on the freeway.
The volume of the gas from full till the light goes on is about 32 l on my car, i.e. the range of 500 - 600 km is very realistic.
There are still some 6 - 7 liters available in the tank after the light switches on (theoretical volume of the tank is 40 l, but I am not sure whether or not it is fully useable).
I tried the range on this reserve once with a full 10-l jerry-can ready, and it was at least another 150 km.