According to Audi the A3 TDI returns an EPA-estimated of 30mpg in the city and 42mpg on the highway. For some reason, Audi thought it would be a good idea to compare the diesel-powered A3 hatchback to the Lexus HS 250h four-door sedan in its press release saying that the Japanese model "offers similar combined fuel economy with hybrid technology, but not superlative highway mileage range."
For what it matters, the 187HP HS 250h, which starts from $34,200 in the States, received EPA-estimated ratings of 35 mpg city and 34 mpg on the highway for a combined 35 mpg.