Fuel economy

Hi all, I've just re-fuelled my newly aquired 93 3.0lt TD SSR-G Surf for the first time and it returned me 12.23 Lt/100km. (8.18km/Lt, 23.11mpg)This was approximately a 50% combination of "normal" city driving and highway/hilly country road driving. (I'm in South Australia)
I travelled 418km from full 'til the needle was almost on the 'E', If you do the sums, (based on 65lt tank)this means there was 14 litres of fuel left. (another 100k's worth) so 500k's + is possible from my machine.

51.12 Litres to fill
418km travelled

Regards,
Michael