[Dazzler]

Sounds like some poor quality control there 

Got the car back Friday and it has been running just swell for almost 200 km. Did an astonishing 3,7 l/100 km on the odo during a 100 km highway ride today. Through a large town and a lot of light crossings. So I'm back as one happy I30 owner.

[Phil №❶]

That's more like it 

[peon2t]

Got the car back Friday and it has been running just swell for almost 200 km. Did an astonishing 3,7 l/100 km on the odo during a 100 km highway ride today. Through a large town and a lot of light crossings. So I'm back as one happy I30 owner.

3,7? Urban driving?
It seems the mechanic screwed up the odometer then...

[Phil №❶]

Perhaps this should be moved to the "Speedo workings" thread then. 

[Doggie 1]

Gee, 3.7 
Mine's not so good afterall.
Maybe I should trade it in again?   

[Asterix]

Got the car back Friday and it has been running just swell for almost 200 km. Did an astonishing 3,7 l/100 km on the odo during a 100 km highway ride today. Through a large town and a lot of light crossings. So I'm back as one happy I30 owner.

Good to hear..

Did they tell you what they did to solve the problem...

3,7? Urban driving?
It seems the mechanic screwed up the odometer then...

No highway and through  one town. I must add that I have 40 psi in my tyres as an experiment. As soon as i entered the town the odo climbed rapidly. On top of that I was doing my best to be economical in my driving (pretty boring).

Good to hear..
Did they tell you what they did to solve the problem...

Yezz, the wire harness leading from the ECU was damaged as it was trapped under the engine cover. This leading to multiple faults.
These faults was stored in the ECU and led to the misbehaving and likely also prevented the engine to run properly. They have repaired the wires. I tend to tell myself that the engine is running more smoothly now.