Don't know what you mean when you say miles per gallon figures are inaccurate, how can dividing the mileage done by the fuel put in be innacurate? It seems we have the same vehicle, Xsara LX Estate HDI 90, though mine's a Y plate, and has done 40,000 miles, probably enough to have run it in. Yet I am unable to better 50 mpg, no matter how gently I drive.