I bought my 2010 Fusion Hybrid in June. It has about 55k miles on it. It's supposed to be getting ~40 hwy/36 city. I drive almost exclusively in the city, but ever since I bought it it's only been getting 32-33 mpg. 

I took it to a mechanic, who basically that I just need to keep driving it and the mpg will go up. It hasn't. In fact, it's been going down. Obviously some of that can be attributed to the cold weather, but I really think it should not be getting as low as 31 mpg.

No warning lights are on. I drive very carefully and efficiently, accelerating slowly and using the EV mode wherever I can. But I can only drive so carefully before I start getting honked at by other folks for driving too slowly. 

Should I just take it to the dealer? Has anyone else had this problem?