The MPG debate, why can't I get the mileage advertised.

[Warmfuzzies]

Plenty of Darwin award winners would argue that they cannot obtain the necessary mpg as advertised by manufacturers, so it shouldn't be any shock to those with a modicum of common sense to realise why; but for those less well able to differentiate life and the laboratory, have a quick look at the attached as a refreshing insight for once.

K.

[spitsfire]

It's not so much 'a refreshing insight' as marketing spin on numbers that are, in essence, wholly artificial and misleading.

It's not uncommon (plenty of posts/threads on PH) to find 30%+ differences between these artificial numbers and real-world fuel consumption.

It's much the same as me saying I could run the 100 metres in 10 seconds*

• downhill with an 80mph following wind on 90% oxygen

[Drive Blind]

is that pic showing an R8 on a 2wd rolling road?
Can't imagine that does the 4wd system much good.

[Krikkit]

spitsfire said:

It's not so much 'a refreshing insight' as marketing spin on numbers that are, in essence, wholly artificial and misleading.

Actually it's the only number they're allowed to quote about economy, nothing to do with spin at all.

[spitsfire]

Krikkit said:

spitsfire said:

It's not so much 'a refreshing insight' as marketing spin on numbers that are, in essence, wholly artificial and misleading.

Actually it's the only number they're allowed to quote about economy, nothing to do with spin at all.

I could be wrong, but it's my understanding that they can quote other numbers, but are required to quote the numbers from the EU standardised testing.

The numbers themselves are misleading, in that they don't reflect real world driving.

The article is spin because it says "your Audi may produce a better or worse result than that of the similar vehicle tested". I've never, ever, achieved the published numbers - I did get reasonably close in a hired Focus a couple of years ago, but that was under perfect conditions on a long drive (98 RON, slightly over-inflated tyres, keeping revs on the floor, steady 55mph). It's worth noting that, to do this, I was being overtaken by trucks and flashed by other cars.

According to the FT, the gap between stated and actual fuel economy of European cars that has soared from 8 per cent in 2001 to 31 per cent in 2013.

The Guardian says carmakers routinely manipulate official UN-backed miles/gallons tests, with a series of tricks including stripping the car down to weigh as little as possible, overinflating the tyres and testing in the thin air at high-altitude tracks.

The Telegraph cites the Volkswagen Polo Bluemotion – a small diesel car – is averaging 65.4mpg in owners' hands, which sounds good until compared with the official test figure of 80.7mpg

In other words, it's total bks. Suggesting there is any real value to the numbers is ridiculous, much like my 100 metres sprint claim.

[sjg]

spitsfire said:

According to the FT, the gap between stated and actual fuel economy of European cars that has soared from 8 per cent in 2001 to 31 per cent in 2013.

In (early) 2001, the only thing that mattered for VED purposes was engine size. The only thing that company car tax was based on was list price and mileage. CO2 and mpg figures (they're linked) were measured as part of the standard testing process for new cars, but the manufacturers didn't worry about it too much because it had no real effect on anything.

Almost overnight, it did matter. A few g/km could knock their cars into a much more favourable tax bracket. When planning new cars, minor changes to things like gearing or choice of OE tyres could get substantial improvements in the artificial tests without affecting how the cars drove. It drove development of better combustion control to make the most of the fuel under light loads. Over time with things like congestion charge exemption and the £0 VED brackets, hitting a low figure became crucial for some models and manufacturers who managed it got great sales as a result - even if that meant ditching spare wheels and the like to do it.

Ultimately though, it's about optimising for a very specific test which doesn't reflect how cars are driven in the real world. The energy needed to accelerate 1200+kg of family hatchback up to speed over and over doesn't change too much, but we're not doing it at 25 degrees ambient temperature with an empty boot and the A/C off. It's useful for comparison between cars only - you have to work out how far your driving deviates from the test to figure out a realistic figure for your own use.

[Warmfuzzies]

sjg said:

It's useful for comparison between cars only - you have to work out how far your driving deviates from the test to figure out a realistic figure for your own use.

At last, someone with a sense of reality.

Of course it's only a tool for comparing apples with apples, and not a definitive of what should be obtained in a real world situation.

K

[Willy Nilly]

I struggle to believe that the UK's VED and BIK system had much influence on how cars and their engines have been developed.

[Mave]

So why are we seeing lots of 4 cyl turbo petrols replacing 6 cyls? Or lots of really small 4 cyl turbos replacing larger NA 4 cyls?

[Willy Nilly]

Mave said:

So why are we seeing lots of 4 cyl turbo petrols replacing 6 cyls? Or lots of really small 4 cyl turbos replacing larger NA 4 cyls?

Are you saying the tax system of a small island nation in the north Atlantic has that much influence on global car engine design? I suspect it doesn't.

[simonh9]

Willy Nilly said:

Mave said:

So why are we seeing lots of 4 cyl turbo petrols replacing 6 cyls? Or lots of really small 4 cyl turbos replacing larger NA 4 cyls?

Are you saying the tax system of a small island nation in the north Atlantic has that much influence on global car engine design? I suspect it doesn't.

Or maybe, just maybe, the whole of Europe (not to mention half the rest of the developed world) is interested in fuel economy and they also have tax regimes and schemes that influence CO2.

[Willy Nilly]

simonh9 said:

Willy Nilly said:

Mave said:

So why are we seeing lots of 4 cyl turbo petrols replacing 6 cyls? Or lots of really small 4 cyl turbos replacing larger NA 4 cyls?

Are you saying the tax system of a small island nation in the north Atlantic has that much influence on global car engine design? I suspect it doesn't.

Or maybe, just maybe, the whole of Europe (not to mention half the rest of the developed world) is interested in fuel economy and they also have tax regimes and schemes that influence CO2.

People are implying that because HMRC said they will set VED and BIK rates based on CO2 emissions, all of the worlds car manufacturers jumped to to attention and re-engineered their engines to suit our system.

[hufggfg]

Warmfuzzies said:

sjg said:

It's useful for comparison between cars only - you have to work out how far your driving deviates from the test to figure out a realistic figure for your own use.

At last, someone with a sense of reality.

Of course it's only a tool for comparing apples with apples, and not a definitive of what should be obtained in a real world situation.

K

The problem is that even this isn't true, as it entirely depends just hoe the manufacturer has set the car up. They could do everything to target the Euro tests, or they could set it up for best real world (or somewhere in between).

So using the official figures even as only a comparison is completely useless.

[mondeoman]

CO2 is the culprit. Manufacturers get taxed on every car they sell for every gram that their fleet average CO2 output is over the industry target, based on a standard test cycle (which is nothing like real-life driving). IIRC its something like £10/car/gm, which can very quickly add up to a lot of money for a volume seller.

They do NOT test with over-inflated tyres, no wing-mirrors, or tape over the shutlines, thats just media stupidity.

The CO2 fleet average is reduced regularly, so big, "uneconomic" V8's can kill a manufacturers fleet average, which is why they are disappearing (and wont come back).

[sjg]

Willy Nilly said:

I struggle to believe that the UK's VED and BIK system had much influence on how cars and their engines have been developed.

The CO2 changes from 2001 were part of a whole load of changes across Europe at around the same time. They were mostly done in the mid-90s - the EU didn't specify exactly how states should tax cars, but most came up with similar ideas given that a standardised test for CO2 was coming.

Many other member states had taxation systems based on any of cylinder capacity, weight or power output (or a mix of those) - and those don't incentivise CO2 (or fuel use) improvements beyond encouraging people to buy smaller cars. Some member states had flat rates similar to the UK.

Almost all now base their taxation on CO2, only a handful of eastern European ones don't. Many have much more punitive taxes for high CO2 vehicles, both for annual charges and also registration. Look at what a high CO2 car costs to buy in Spain or Portugal or Ireland and you can understand the desire for the car manufacturers to squeak under arbitrary targets.

European market is still about a million cars a month even though it's been in decline. The manufacturers can't afford to ignore it, and they know full well that similar taxation schemes will be coming to other nations they want to sell into as well.

[anonymous-user]

For some reason, car owners seem to think that buying an efficient car is all that is required to get good fuel economy.



Here is a violin, a very very expensive one:





If i bought that^^^, played it and said "it's hopeless, it sounds awful" you'd rightly think i was an idiot, and yet every day, millions of people with no training, skills or aptitude for driving, for some reason think that their cars should "magically" return amazing fuel economy...........

[AW111]

It can be done if you try hard enough :

I used to live in the country miles from anywhere, and drove home from Mebourne one Christmas eve, late.
When I found that my usual fuel stop was closed, and realised that he next one (150 km away) may well be closed by the time I got there, I went into total hypermiling mode. It's amazing how far you can stretch a small amount of fuel when you really have to.

It's tiring, and would annoy hell out of anyone else on the road, but there was basically no traffic that night, and with the aid of the emergency fuel can I got home, at some stratospheric fuel economy compared to usual.

[Jader1973]

Based on some of the discussions I've been involved in my understanding of the test is that it is done on a rolling road which is set to simulate the resistance of the actual road based on the weight of the car. However, they don't use the actual weight of the car, they use a weight class which covers a range of weights. I can't find them online but for arguments sake say they span a 100kg range e.g from 1000kg to 1099kg. They use the same setting for all cars in that weight class.

If your car is at the bottom of the range that is bad, if it is at the top of the range that is good.

If a car is at the bottom end of a particular weight bracket that is when things like cans of goo instead of spare wheels appear as standard equipment to try and drop the weight down in to the next weight bracket, hence improving fuel consumption.

The fact a spare wheel is a no cost option and everyone asks for it and therefore tips their car over the weight limit is irrelevant

[thegreenhell]

Meanwhile in America... Hyundia and Kia have recently received record fines for overstating the fuel economy of some of their vehicles. On top of that, they faced a civil class-action lawsuit from the owners of the affected vehicles, meaning that they are now reimbursing all owners the cost difference between their claimed mpg and the real-world mpg, plus an addition 15% compensation on top.

http://www.bbc.co.uk/news/business-29887117

[Warmfuzzies]

America and litigation shocker, no surprise there then.