Hi Beeno, welcome to Civinfo
3000 rpm is a lot for this engine, I guess your previous car was a petrol?
The general rule with a turbodiesel: apart from driving on from standstill, take one gear higher as you would on a petrol in the same speed range. I often accelerate quite swiftly in 1st gear from standstill (not spinning my wheels but swiftly) then change to 3rd at some 30 km/h and to 5th at 45-50 km/h, on longer city strips I add my "VAT" to the allowed 50 km/h and at some 58 km/h displayed (maybe 55 km/h real speed) I go on with 6th, as long as there are no steeps to take it's no problem, really. I know this would murder a petrol engine but with a high-torque diesel it's OK. The skipping of gears also saves fuel (and the clutch).
On the Autobahn - if I'm not in a hurry (or in a mood for low-flying
) limiting speed to 150 km/h is very economical (130 would be more economical but then some old van might honk at you to go faster).
Using the cruise control will save you another 0,5 l/100, whereas turning off the aircon brings no (measurable) savings.
With the above tips, you should get between 5,5 and 7 l/100 km
it's still not as good as it gets (my best value was about 4,6 or 4,8 I don't remember exactly) but this is possible only with really lame driving and it's not what the Civic was made for is it?
Cars with smaller engines and less weight will have better economy still, but one can't have everything...