How many miles per gallon for Rover 600 series L Reg?

I have just bought an L Reg Rover 620i and I was wondering if anyone knows what the fuel usage is like. How many miles can the car cover on a gallon of fuel. The car has got a 1.8 engine capacity.|||If it is a 620i, then the engine is a 2 litre not a 1.8 . The 820 I had returned about 22 round town %26amp; around 40 on a good run. With around 140 bhp on tap it can 'run away 'with the fuel if you give it the beans ! Enjoy a very under-rated car while you can.|||realistically about 30 mpg if you are lucky, we owned one but sold it|||About 20 miles in town and around 35 on a motorway..