Hi Eamon,

That car's engine is known for being pretty economical so it certainly sounds like there's something up. The easy things to check first are that your tyre pressures are correct (too low and they cause extra drag); your wheels are correctly aligned (misalignments cause drag); you don't have a roof rack or box or bike rack permanently fixed; your rear window demister isn't permanently turned on; and your boot/back seat isn't full of anything heavy when it doesn't need to be.

Next thing to do is get the car serviced. A dirty air filter alone could cause a drop in economy, but it's a good idea to change the oil and filter and the fuel filter too if it hasn't been done in a while.

If none of this makes a difference then there may well be something else awry, with the injection system or possibly the air flow measurement. If that's the case then the car needs to be hooked up to a diagnostic machine to see if you can work out what the issue is.

Best of luck.