We have our regularly maintained 2004 VW Jetta Turbo and noticed in the past month or so the mileage on our car has significantly decreased.

The car only gets about 300-350 KM in the city (unleaded) whereas before it used to get 100 Km per tank more....

The mystery is the fact it's reguarly maintained, brakes/air filter were all replaced and tire pressure is fine.....no engine light has appeared (discounting MAF/02 sensors)......

We are thinking to get some engine cleaner (to remove carbon buildup) and use premium gas...and replace spark plugs.....

ANY SOLUTIONS TO OUR MYSTERY? Anybody else go through this?