I have a vRS and my wife has a Seat Leon 1.8T Sport, both have the 180bhp turbo engine, even have the same engine codes. Both cars have done less than 30K and both are regularly serviced.

Fuel economy on the Skoda is around 35-38 on a long run at 80 ish, on the Seat it is 32-34 at the same speeds. Any ideas why?

Is the gearing in fifth the same on both cars?

IIRC the Octy has a slippery shape and good CD figure (something like 0.29)

Could make a difference?

Do they both have the same sized fuel tank ?

Could be any number of other factors too. Different driving styles for any given person in each car is one that springs to mind.

Could different gear ratios be a factor?

The gearing is the same in top gear, even though the seat has a 6 speed box, as the revs in top for a given speed are the same in both cars. The consumption figures given are for when I was driving both cars, though not at the same time.

Must admit, fuel consumption more like 30mpg when my wife drives.

I think the Skoda has better aerodynamics than the Seat. Seem to remember reading somewhere, something about that.

I think Matt was right... a combination of gearing and aerodynamics.

Offcially the RS does approx 35mpg and the Cupra 32mpg (IIRC).