True MPG vs Claimed (in the UK)
Discussion
Am I right in thinking that in the UK, manufacturers will soon have to publish TRUE MPG rather than the current CLAIMED MPG which we all know is nowhere near the truth. I know in the USA the official government figures are TRUE MPG, not the silly figures published by manufacturers we see here in the UK. It does seem daft that to find the truth you have to check out the US gov website. I do hope I have heard right.
The only thing I'll say is be careful what you wish for. These tests also generate a car's emissions figures which are used as a basis for taxation for private and company cars.
Any new test that's likely to produce 'real world' consumption figures might well also produce 'real world' CO2 emission figures, which we probably won't like.
Any new test that's likely to produce 'real world' consumption figures might well also produce 'real world' CO2 emission figures, which we probably won't like.
GroundEffect said:
They aren't the OEMs claims, they are the output from the industry standardised test!
The test is what needs to change and it will be over the next few years.
this ^^^^The test is what needs to change and it will be over the next few years.
you can whinge all you like about the figures, but that's what they are legally obliged to publish.
if you want to blame somebody, try the politicians that came up with the legislation in the first place.
Goggy said:
Am I right in thinking that in the UK, manufacturers will soon have to publish TRUE MPG rather than the current CLAIMED MPG which we all know is nowhere near the truth. I know in the USA the official government figures are TRUE MPG, not the silly figures published by manufacturers we see here in the UK. It does seem daft that to find the truth you have to check out the US gov website. I do hope I have heard right.
Define true.Goggy said:
Am I right in thinking that in the UK, manufacturers will soon have to publish TRUE MPG rather than the current CLAIMED MPG which we all know is nowhere near the truth. I know in the USA the official government figures are TRUE MPG, not the silly figures published by manufacturers we see here in the UK. It does seem daft that to find the truth you have to check out the US gov website. I do hope I have heard right.
no you're wrong.US (EPA) figures are obtained in the same way, ie, a std drive test on a set of rollers in a test cell.
yes, they use a different drive cycle, (from EU) but it's pretty much the same deal.
http://www.epa.gov/fueleconomy/documents/420f14015...
Goggy said:
Am I right in thinking that in the UK, manufacturers will soon have to publish TRUE MPG rather than the current CLAIMED MPG which we all know is nowhere near the truth. I know in the USA the official government figures are TRUE MPG, not the silly figures published by manufacturers we see here in the UK. It does seem daft that to find the truth you have to check out the US gov website. I do hope I have heard right.
What on earth do you mean by "true" and "claimed"? 
Both numbers are the result of the car being run through a standard test by an independent body. The tests are different and the US one arguably gives a more accurate result (although I wonder how much of that is down to European manufacturers putting more effort into fooling the test than US ones) but there no fundamental difference between the two.
Even if the manufacturers could come up with a more realistic test and more "accurate" numbers, they wouldn't be allowed to publish them.
It is about time we had an overhaul of the NDEC test though, it has become something of a joke and is, IMO, pushing the whole European car industry in the wrong direction from both an environmental point of view and a running costs ones. The test needs to be much longer and more varied to make it harder to tune engine maps to it at the expense of MPG in other situations.
Edited by kambites on Monday 3rd August 08:41
As other people have asked, what do you mean by true MPG? What's true for a car spending all day in city centre traffic will be very different for that same car doing 50mph all day on a straight flat road.
The biggest issue I have with the current system is that it skews the figures massively in the favour of hybrid vehicles. If your car can do 90% of the test on electric power alone, it can report a figure of 150mpg! (Mitsubishi Outlander PHEV springs to mind). It the test was 4 times as long that figure would be nowhere near as impressive.
Incidentally I picked up a 1.6 turbo petrol car last weekend, and on the 60 mile gentle drive home the trip computer was showing 4mpg over the official economy figure. Most cars can hit the official figures when driven gently.
The biggest issue I have with the current system is that it skews the figures massively in the favour of hybrid vehicles. If your car can do 90% of the test on electric power alone, it can report a figure of 150mpg! (Mitsubishi Outlander PHEV springs to mind). It the test was 4 times as long that figure would be nowhere near as impressive.
Incidentally I picked up a 1.6 turbo petrol car last weekend, and on the 60 mile gentle drive home the trip computer was showing 4mpg over the official economy figure. Most cars can hit the official figures when driven gently.
Edited by IanCress on Monday 3rd August 08:51
IanCress said:
Incidentally I picked up a 1.6 turbo petrol car last weekend, and on the 60 mile gentle drive home the trip computer was showing 4mpg over the official economy figure. Most cars can hit the official figures when driven gently.
On a long out-of-town trip it should be doing the extra-urban figure though, not the combined. The NDEC overall figure is meant to represent a roughly 50:50 mix of stop-start city traffic and A-road driving (by distance, so significantly skewed towards urban driving by time). 
In other words you should get the official figure if you spend 40 minutes driving around a city centre then 20 minutes on the open road.
Edited by kambites on Monday 3rd August 09:00
kambites said:
On a long out-of-town trip it should be doing the extra-urban figure though, not the combined. The NDEC overall figure is meant to represent a roughly 50:50 mix of stop-start city traffic and A-road driving (by distance, so significantly skewed towards urban driving by time).
In other words you should get the official figure if you spend 40 minutes driving around a city centre then 20 minutes on the open road.
True, in which case it was about 4mpg under the extra-urban figure, which i'm pretty happy with.In other words you should get the official figure if you spend 40 minutes driving around a city centre then 20 minutes on the open road.
kambites said:
It is about time we had an overhaul of the NDEC test though, it has become something of a joke and is, IMO, pushing the whole European car industry in the wrong direction from both an environmental point of view and a running costs ones. The test needs to be much longer and more varied to make it harder to tune engine maps to it at the expense of MPG in other situations.
the problem is the test cycle was never designed to be used in the way it is now, when it was devised, CO2 output was not the target (and arguably still isn't for the testers), it's all about CO, HC, NOx emissions.then governments started legislating on CO2 both as a driver for car tax, and also fleet averages etc, so, what do you expect the manufacturers to do? They, quite logically, worked on making the cars perform well in the test.
Worth mentioning, the current test is not just a few miles, it's 20 minutes and ~11Km long, made up of 4 cycles of the Urban Driving Cycle ECE-15 + one Extra-Urban Driving Cycle, top speed is 120Kmh.
depending on the test standard (EU1,2,3,4,5,6) defines the start/stop procedures and what the limits on gas outputs are.
True, but from what I remember it's 20 miles during which the car is either maintaining constant speed, accelerating at about 0.05g or decelerating at about 0.05g. Hardly representative of the mix of situations in real driving. You'd annoy a lot of people if you drove like that. 
I think it should be viable to run the test over, say, a couple of hundred miles with a genuine variance in rates of acceleration and deceleration and some long runs at a constant 70-80ish.
I think it should be viable to run the test over, say, a couple of hundred miles with a genuine variance in rates of acceleration and deceleration and some long runs at a constant 70-80ish.
Edited by kambites on Monday 3rd August 09:16
Scuffers said:
GroundEffect said:
They aren't the OEMs claims, they are the output from the industry standardised test!
The test is what needs to change and it will be over the next few years.
this ^^^^The test is what needs to change and it will be over the next few years.
you can whinge all you like about the figures, but that's what they are legally obliged to publish.
if you want to blame somebody, try the politicians that came up with the legislation in the first place.
No doubt if a new test is brought in there will be a change to the software on new cars which will mean pre and post cars will score different figures on the same (new) test.
kambites said:
True, but from what I remember it's 20 miles during which the car is either maintaining constant speed, accelerating at about 0.05g or decelerating at about 0.05g. Hardly representative of the mix of situations in real driving. You'd annoy a lot of people if you drove like that.
I think it should be viable to run the test over, say, a couple of hundred miles with a genuine variance in rates of acceleration and deceleration and some long runs at a constant 70-80ish.
it;s not that static a test, the cycle details are on Wiki https://en.wikipedia.org/wiki/New_European_Driving...I think it should be viable to run the test over, say, a couple of hundred miles with a genuine variance in rates of acceleration and deceleration and some long runs at a constant 70-80ish.
also, if you made it 200 miles, how is that representative? most journeys are typically short and from cold start, if the test was 100+ miles, it would be much easier to meet the targets.
Look, I don't disagree the test has outlived it's purpose, but the rationale behind it is still very valid.
Hackney said:
But the manufacturers' have been guilty of playing the system by introducing more and more gears or writing specific software which is based around the test.
No doubt if a new test is brought in there will be a change to the software on new cars which will mean pre and post cars will score different figures on the same (new) test.
you can't blame the manufacturers for making cars that optimise the test results, their sales, tax, etc are all based on this test so it would be commercial suicide for them not to make cars excel on said test.No doubt if a new test is brought in there will be a change to the software on new cars which will mean pre and post cars will score different figures on the same (new) test.
like I said before, the test is not the problem, it's how it's used in legislation that creates the problems.
I would argue that if you dump the emissions targets, you could end up with more economical cars with overall lower emissions.
Scuffers said:
you can't blame the manufacturers for making cars that optimise the test results, their sales, tax, etc are all based on this test so it would be commercial suicide for them not to make cars excel on said test.
like I said before, the test is not the problem, it's how it's used in legislation that creates the problems.
I would argue that if you dump the emissions targets, you could end up with more economical cars with overall lower emissions.
I don't care whether you call it the test or the way it's used, that's just a linguistic argument. The test is not fit for purpose and, given the current political climate, that purpose is not going to go away so the test needs to be changed (or replaced with something else for the purpose of measuring CO2 emissions, if you want to keep it for other things). like I said before, the test is not the problem, it's how it's used in legislation that creates the problems.
I would argue that if you dump the emissions targets, you could end up with more economical cars with overall lower emissions.
I wasn't suggesting making it longer to make it representative of a typical journey; I was suggesting making it longer to enable it to be more varied.
Edited by kambites on Monday 3rd August 09:48
Gassing Station | General Gassing | Top of Page | What's New | My Stuff