Originally Posted by
RichieST
Car manufacturers try really hard to get their cars to be as economical as they can. If they could make it 25% more economical for only 200 euros then they would have done it from the factory.
Except diesels, where the manufacturers hands are tied by EU legislation regarding emmisions. Modern diesels are mapped from the factory so the fuel is not burned 100% but the emissions are low. We never check diesel emissions after the car is built, so you map it to run more efficiently, and ignore the EU emissions restriction, and you have more mpg and performance.
25% gain on a petrol? no chance.