I replaced my old Audi A3 1.6 petrol with a 2-year-old Audi A4 TDI 2.0 with the new CR engine, primarily to get a much more economical car. The figures for combined economy should be around 50mpg and motorway about 60mpg. I actually get a combined consumption of 36mpg and recently tried a motorway stretch driving at exactly 70mph and got a consumption of 45mpg. This is way out of the EC figures and had I known this I would have not bought the car. It is still under manufacturer's warranty. Is there anything I can do to get Audi to investigate the issue or compensate me for false claims of fuel economy?