Nevermind then…
I have successfully passed the technical inspection. I’ll now be able to concentrate more on my mods.
I have tested the maximum size of tire I could mount. I put on a 155/80 R14 junk tire which is 10,3% bigger. When I steered to the maximum, there were just a few millimeters free between the tire and the inside of the wheel well. But the rims I will mount have a bit more offset, which will put them more outside. On the pics, the car is not on level, that's why it's so high.
I have redone the graph with more realistic figures of consumption gain based on the Lupo 3L official curves. The ratio (FE gain/gear ratio gain) is 0,55 from 3rd to 4th and 0,58 from 4th to 5th. I’ve considered 0,55 vs 0,75 before. This change give less advantage to big tires. In red, the tires that won’t fit. I also added, just to compare, a 185/60 R15 tire rated A which comes out as best. But to mount them, I need new rims and new brake discs for hole spacing, so that’s not worth it.
Conclusion : I’ll give a chance to the Ecocontacts 175/70 R14 (I want the biggest RPM reduction). They are available in extra load which, I think, is good for rolling resistance (max. pressure is 3,5 bar vs 3 for normal version).
Edit: and I have also filled all my fillup data.
http://ecomodder.com/forum/em-fuel-l...vehicleid=6831