Lower miles per gallon on an Audi A5?

Hi, I have a 2008 Audi, it has been maintained properly and generally has not given me much problems. However, over the last couple of months I have noticed that my MPG’s have gone down about 20-25%. Do you know what could cause this? I have heard about problems with build-up in this car’s FSI fuel injection system. Could that be it, and if so, how do I get it fixed? I took it to the dealer and they said they can’t tell anything is wrong. Thank you!

Find an Audi forum, ask around there. This is a very specific question about a new (FSI) system.

Have you been using Top Tier Gasoline? http://www.toptiergas.com/ If not that might be the problem.

If there’s not enough detergents in the gasoline, and on a direct injection fuel system, deposits can easily form on the orifices on the injectors effecting fuel mileage.