Fuel Economy Figures and Actuals - Sale of Goods Act

Ultrasonic

NatWestCustomer wrote: »

The context is that I bought a new car and chose it because of its efficiency figures. Now it's brand new and I'm a realist on the old manufacturer testing numbers versus real life but I'm getting 37.3 on a car that's extra urban is supposed to be 67.3 (my commute is mainly motorway). I've had it for less than a month.

What is the car, and is it brand new? Have a look here to see what other drivers are getting to give you some idea of if their may be an issue with the car:

http://www.honestjohn.co.uk/realmpg/

Bear in mind that the extra urban driving cycle does not represent motorway driving (the average speed for this part of the test is just 39 mph). I think if manufacturers quoted a fuel econonmy figure for, say, a 70 mph steady speed this would be more helpful, but they don't. To get a good idea of how the tests are carried out, have a look at the 7th video down on this page, called 'Fuel Consumption Figures Explained':
http://www.audi.co.uk/owners-area/tutorials.html

For a quick look at what the test cycle is, see here:
http://en.wikipedia.org/wiki/New_European_Driving_Cycle

Your 37 mpg figure doesn't sound great though. As others have said, if the car is brand new then give it a chance to run in before worrying too much. Also, if you do a lot of motorway driving then speed has a big impact on economy. Slow down and your mpg will go up.

Ultrasonic

Jamie_Carter wrote: »

If you accelerate harder, or go up and down hills, then this will all have an impact on your consumption.

Good point re. hills, which will definitely reduce fuel economy. Hard (high load) acceleration is usually more fuel efficient than slow acceleration though (Google BSFC). The trick is to avoid unnecessary acceleration. Accelerating hard to then end up braking wastes fuel.

Ultrasonic

IanRi wrote: »

There's also obviously a sweet spot for the revs...

Actually there generally isn't a sweet spot. Generally speaking, for steady state driving, you'll get best fuel econonmy going as slow as you can in top gear without lugging the engine. (I don't have time to dig out links now.)

FreddieFrugal

Ultrasonic wrote: »

Actually there generally isn't a sweet spot. Generally speaking, for steady state driving, you'll get best fuel econonmy going as slow as you can in top gear without lugging the engine. (I don't have time to dig out links now.)

This is true but I found - for instance that keeping in third as opposed to moving into 4th before 40 mph kept mpg up higher than shifting early. Same with shifting into 5th before 50mph.

But yes if you're on a long flat road then shift into highest gear possible for best results.

mad_rich

I actually get more than the quoted figures for mpg on my Fabia, as do most other drivers

http://www.honestjohn.co.uk/realmpg/skoda/fabia-2000/19-tdi

but I gather that's a bit of an outlier.

If you think the figures are unrealistic, I think it's probably the EU testing process you need to attack, rather than the manufacturer. They're just (quite reasonably) trying to make their car get the best possible figures while sticking to the test process.

Hintza

If you want the real figures then you must be prepared to pay increased VED. These "offical figures" are the same for all car manufacturers so should just be used as a guide.

neilmcl

New VW Golf by any chance?

OddballJamie

My money is on the OP having the new Ford EcoBoost engine, people have been getting shocking returns on them. Same thing happened with the Fiat 500 Twinair.

2010

IanRi wrote: »

Same with shifting into 5th before 50mph.

I have a Fiesta,18 months old, with a green pointed arrow indicator on the speedo which comes on to tell you to when to change gear.
This lighted green arrow comes on at just over 40mph to change from 4th to 5th.(2500 rpm)
Ford also state in their manual and on their website (tips for saving fuel) the optimum time to change gear is 2500 rpm.

Cornucopia

There seems to be some confusion early in the thread about age and its effect on economy.

For diesels, full economy won't generally be reached until the car has a healthy number (few 1000s) of miles under its (cam)belt. Unless there is something wrong with the car, the economy shouldn't deteriorate much at all over its lifetime.