I have just changed from standard 205/50/R17's to 225/45/R17 Pirelli P Zero Rosso's, they seem good but my average fuel economy has dropped from around 35mpg to less than 30. Has anyone else experienced this level of drop when changing tyres?

I am running Michelin Pilot Sports on 225/45 17, instead of the Conti's 205/50 17 that mine came with. Cant say I have noticed any change in the mpg and still get mid to high 30's. Are the tyre pressures correct, low pressure will cause more friction/heat and reduce the fuel economy.