I think the priotities for improving are perhaps in terms of priority based on costs:
1) Change filters
2) Change spark plugs
3) new oil
4) Perhaps change luftmassemätare
5) read codes.
I guess no 5 is nothing I can do myself. I think it's a scandal that something that may have such a substantial effect on petrol consumption is not accessible to ordinaary/normal drivers.
On the web site, it seems it's not possible to reply to a specific mail, so its good you can see I am trying to involve you. And you have been geneous so far!
Another scandal I will take up at some time. Why do almost all car manufacturers have different degree of magnification on their mirrors. So if you look in one, you may think thre object is 10 meters behind , and in another 25 metres.
And to be personal, this is the reason I had a serious car crash that stole 2 years of my life, putting me in a wwheel chair. I will do something about it. Believe me!!
Brian
PS Hope this language is even easier to understand.