Fuel Economy Figures and Actuals - Sale of Goods Act

Mobeer

2010 wrote: »

Of course it doesn`t as long as the tank is completely empty when you fill it and take note of exactly the amount you put in and run it to completely empty and note the milage.

You did do this, didn`t you?

That's the wrong way around - you will never know when the tank is completely empty.

Instead, start with the tank completely full, drive until near empty, and refill. Then the calculation is much easier.

Cornucopia

Mobeer wrote: »

That's the wrong way around - you will never know when the tank is completely empty.

Instead, start with the tank completely full, drive until near empty, and refill. Then the calculation is much easier.

Exactly. :beer:

Joe_Horner

Cornucopia wrote: »

The miles per tank doesn't lie.

Over a single tank it can because the capacity quoted by manufacturers isn't exact - typically it's within about 5%, which is 40 miles either way over 800 miles. It can also "lie" depending on exactly how you fill, how level the forecourt is, and how sensitive the auto shut-off is in the particular pump you use.

None of the above will make a huge difference, but can easily add up to 3 or 4 mpg between them over a single tank.

GolfBravo wrote: »

And don't forget to ask the manufacturer for the "alternative" ECU software that they use for these official tests - the engine will not last very long, but the fuel economy will be amazing.

Oh, and you need to drive your car in a manner perfectly matching the fuel test environment, and preferably leave your car on the chassis dynamometer, and just pretend to drive. And remember, low powered vehicles don't even have to reach 56MPH for the Extra Urban Driving Cycle - so on a motorway you should stay in the slow lane and drive at 55mph.

Also disconnect your alternator to remove the electrical chargig load and, whatever you do, do NOT run the aircon or heater (robs power / lowers engine temp respecively) and do NOT open the windows (all that drag!)

Effectively, the tests, and the rules of what's allowed in them, are a complete joke which have been developed purely to aid the makers in selling cars and governments in setting "green" taxes.

CO2 emissions (if you're worried about a little plant food in the air) are exactly the same as fuel consumption, just expressed in different units so, as your fuel consumption aries widely (and nowhere near the quoted values), so does your CO2 output - if your real life mpg is only 50% of the quoted then your CO2 output is double the quoted.

Yet we base taxes and judge people's eco-morality on these meaningless figures!

GolfBravo

Joe_Horner wrote: »

Also disconnect your alternator to remove the electrical chargig load and, whatever you do, do NOT run the aircon or heater (robs power / lowers engine temp respecively) and do NOT open the windows (all that drag!)

Yes! Sorry, forgot to mention the basics of the fuel EU tests: alternator off, a/c off, lights off, radio off.

Joe_Horner wrote: »

Effectively, the tests, and the rules of what's allowed in them, are a complete joke which have been developed purely to aid the makers in selling cars and governments in setting "green" taxes.

The whole industry is currently focused on low CO2 (fuel) emissions. 1.2 turbo charged diesels with direct injection, and all the other nonsense, are not designed to give you more driving pleasure, they are designed to maximise manufacturer profits. From around 2000 to 2005, the main car manufacturer issue was reliability - cars were just too reliable, consumers didn't buy enough spare parts, and kept their cars for too long. So now you have ultra low fuel consumption and emissions (in a test lab), but then you get hit with a £1500 turbo replacement cost.

OddballJamie

GolfBravo wrote: »

Yes! Sorry, forgot to mention the basics of the fuel EU tests: alternator off, a/c off, lights off, radio off.


The whole industry is currently focused on low CO2 (fuel) emissions. 1.2 turbo charged diesels with direct injection, and all the other nonsense, are not designed to give you more driving pleasure, they are designed to maximise manufacturer profits. From around 2000 to 2005, the main car manufacturer issue was reliability - cars were just too reliable, consumers didn't buy enough spare parts, and kept their cars for too long. So now you have ultra low fuel consumption and emissions (in a test lab), but then you get hit with a £1500 turbo replacement cost.

Are you kidding me, I had a 2004 Peugeot diesel, most unreliable anything I've ever owned.

I know people who had Golfs from those years and they were unreliable too.

2010

Mobeer wrote: »

That's the wrong way around - you will never know when the tank is completely empty.

Instead, start with the tank completely full, drive until near empty, and refill. Then the calculation is much easier.

Easier but probably inaccurate.
If people want to believe the industries figures that`s up to them.
Most people who have seen how they are arrived at are sceptical, to say the least.

As I said earlier modern cars have all the info on them and the mpg reading are well down on the manufacturers.

It`s a pity the program isn`t available on the i player to see how it was investigated.

Cornucopia

2010 wrote: »

It`s a pity the program isn`t available on the i player to see how it was investigated.

I would put money on our discussion here being more detailed, more relevant and more informative.

edit: I remember watching it now. Kind of Watchdog-lite.

2010

Cornucopia wrote: »

I would put money on our discussion here being more detailed, more relevant and more informative.

I doubt if anyone here has ever been invited to a manufacturers place of testing to witness how it`s done.

The figures are way above what you can actually achieve because of the strict testing criteria.

Cornucopia

2010 wrote: »

I doubt if anyone here has ever been invited to a manufacturers place of testing to witness how it`s done.

The figures are way above what you can actually achieve because of the strict testing criteria.

Funnily enough, that's what the program said.

Sorry, but ultimately you get what the car is capable of, whilst being able to influence it to an extent through driving style. If people are disappointed that the latest cutting-edge tech is not giving them the promised level of economy then don't buy cutting edge - stick to proven small diesel engines probably of French manufacture, and (a) enjoy, and (b) accept that you may not get back in economy what you pay in purchase price premium.

Ultrasonic

2010 wrote: »

As I said earlier modern cars have all the info on them and the mpg reading are well down on the manufacturers.

It`s a pity the program isn`t available on the i player to see how it was investigated.

I caught the end of that programme, where they pretty pointlessly strapped a fancy monitoring system onto a Focus to show that they got lower fuel economy than the manufacturers claimed. They could have achieved the same thing without any fancy kit at all, by simply driving further and measuring mpg the old fashioned way. Just as the many, many people who have submitted data to the Honest John Real MPG have done.

BUT I don't think that the NEDC test results are useless, since they do allow comparisons between cars of the same age. Also, the issue is not so much with the manufacturers as the test cycles themselves, which don't seem very representative of how anyone actually drives. The extra-urban part in particular, since most people assume it relates to motorway driving, when it doesn't.

Where there does seem to be a problem is that it is now much harder to achieve the combined mpg that it used to be, which makes comparing data between cars of different ages difficult. Driving economically in my 8 year old Octavia, I do average close to the official combined fuel economy, and on a long run have come close to the extra-urban figure by sticking to a 60 mph maximum speed (best tank 65.9 mpg vs extra urban figure of 67 mpg). I also averaged close to the combined mpg figure on the Megane I had before that. But going by the Honest John site, it does seem increasingly hard to acheive this.