Because of the differences when filling the tank, to get an accurate result is necessary to examine the data during a long distance, or consider some consecutive full tanks.
Last september I went from Barcelona to Luxembourg for the Mercedes-Classic Days in my 230 SL, covering 2.848 km in 5 days (= 308,9 fuel liters and 2,85 oil liters), so the results should be accurate enough:
Average fuel consumption: 10,84 liters per 100 km (=9,23 km per liter)
Average oil consumption: 1 liter per 1000 km
Cruising speed on the highway: 110-130 km/h
During the trip, partial consumption readings went from 8,86 to 12,85 liters per 100 km., so you can see the big influence of the tank refueling in short distances.
Some relevant data:
Model: 230 SL manual 4 speed, 3/75 rear axle
Tyre size: Original (185 HR14)
Engine rebuilt (and adapted for unleaded fuel) just 3.700 km before the trip
Oil: Castrol 20w/50
Fuel: Unleaded 98
Regards,
Albert de la Torre Chavalera
Barcelona (Catalunya/Spain)
Feb.'64 230 SL Euro 113042-10-002432