I am averaging 10l/100km with 70/30 highway and traffic,
Weekend driving goes up to 12,5l/100km
it's high for these current times (liter cost of R16.08),
My manual CI (325 as well) gets below 9l/100km with moderate driving
And around 9,5l/100km with spirited driving,
The advise I would give based on my reading, research and general knowledge: get a 2003 upward* 330i if keen on an e46 6 cylinders vehicle. They come with a 6 speed gearbox and have low end torque as well thus overall better economy.
*more knowledgeable person will confirm the specific year, might be from Oct 2002 - to be safe, I'd go for 2003 upwards.