[saltcured]

Your use of the word "petrol" makes me wonder if you are aware of the difference between US gallons and UK/imperial gallons. UK gallons are larger volume and so give a higher MPG metric for the same vehicle.

There also are not many sub-compact cars marketed in the US, and the range of engine options is usually limited compared to similar vehicles marketed in Europe and the UK. Compacts like a Civic or Corolla would be considered efficient commuter vehicles by most people here, and might get around 40 MPG (US) in highway cruising and somewhere in the 30s as a combined figure (for non-hybrids).