Ford Focus (14-): Discovering Diesel Discrepancies

  • We delve into our Focus' fuel economy
  • Ford says 74.3mpg should be possible
  • Find out whether it's living up to its claims

Ah, the myth of ‘claimed fuel economy’. It’s the bane of our lives as writers trying to help you, the new car buyer.

The reason is that frankly, they’re not what you can expect from your car during normal use. We’ve seen first-hand anywhere between 15 and 30 percent discrepancy between real and claimed figures once we’ve crunched our own numbers.

Sure, the numbers quoted by manufacturers are a decent benchmark for comparing one car with another, but what if you actually care how many miles you’ll get per gallon of (extremely expensive) petrol or diesel?

In the interests of science – or perhaps to sate your curiosity – I thought I’d take a long, hard look at how our Focus is performing. You see, my spec sheet from Ford states the combined average fuel economy as measured using the New European Driving Cycle (NEDC) test common to all car companies is a whopping 74.3mpg. Just how close to reality can this be?

The way I intended finding out was to brim a tank of fuel and calculate exactly how much I use over a period of mixed driving. When noting the miles I’d covered with this amount of diesel I was able to work out exactly what my fuel economy was. I could even work out how much the Focus is costing me per month in fuel if I really wanted a scare. In the interests of giving the car a true test, I also reset the trip computer to see what it claimed to be doing.

Did I wear a white coat for this test? No. But I wanted to.

So without further ado, here are the numbers: I brimmed the tank. I then proceeded to drive for another 291 miles of mixed driving, and then topped the tank up again. The car swallowed 26.5 litres and cost me £33.02.

That equates to 48.22mpg exactly, costing 11p per mile in diesel.

Interestingly, this doesn’t quite stack up with the trip computer, which claimed 54mpg over the same period. It isn't a massive difference, though, in the great scheme of things. 

It’s also quite a way off the claimed average fuel economy of 74.3mpg. In fact, it represents just less than 65 percent of Ford’s figure, meaning we’re losing 35 percent of the possible efficiency if you can replicate the NEDC test.

Since this car has a 53-litre tank, that’s a possible £22 we’re missing out on per tank of fuel.

Maybe I’ll try and drive a little more efficiently and see how much of that I can get back. As I've mentioned in previous updates, the gearing is such that this is a great car to drive at lower speeds, but at 70mph it's sitting at fairly high revs so won't be great on fuel.

Still, at least it's not difficult to actually fuel-up. Ford's brilliant Easy Fuel device means only a diesel nozzle will actually fit, so there's no chance of sticking petrol in there by mistake. Just make sure you follow the three simple instructions if you don't want fuel dribbling down the side of the car or onto your shoes.

Mileage: 4,633

Fuel economy: 48.22mpg