posted 5 years ago

New Rule Kills Confusing MPG Adverts

Official fuel consumption figures might not be replicated on the road

Motor manufacturers must emphasise that official fuel consumption figures might not be replicated on the road following a ruling from the Advertising Standards Authority. Why? Because the regulator – that ensures consumers are not confused/misled – has upheld the complaint of an Audi A3 owner who could not achieve the car's advertised average fuel consumption. Whereas the manufacture acted within the law – and consistently with other producers – the Advertising Standards Authority concluded that it “should have qualified the figure to make clear to readers that it was based on an EU test for comparative purposes and may not reflect real driving results”. This ruling effects all car producers and its influence will be seen via outlets such as television, radio, magazines, and the internet. But let us be clear. It is not that vehicles cannot hit their reported fuel consumption figures – but they must be piloted efficiently and within limited parameters.

Advertising Standards Authority Comments

Advertising Standards Authority spokesman, Matt Wilson, said: 'This is a significant ruling that draws a line in the sand - it is not just about Audi. It sets a precedent that will have ramifications for other car manufacturers. The ruling sets out quite clearly that qualification is needed when quoting this type of figure. There will be an industry-wide communication to manufacturers and trade associations so they are aware of what to expect in future.”

How Is Fuel Efficiency Calculated?

Fuel efficiency is calculated via the urban and extra-urban test cycles. The former replicates motoring through town whereas the latter reflects faster conditions. As such the test vehicle - that must have covered at least eighteen-hundred miles – is placed on a rolling road in a laboratory that has a temperature of between twenty and thirty degrees centigrade. Its engine must not have run for several hours. The urban cycle test requires the car to accelerate, maintain speed, decelerate and idle. During this two and a half mile run it reaches thirty-one miles per-hour and averages twelve. The extra-urban test follows immediately afterwards. This too requires the vehicle to accelerate, maintain speed, decelerate and idle but this time it averages thirty-nine miles per-hour and hits seventy-five throughout a longer route. Results are then averaged to create a combined figure that can be a useful marketing tool. However, as some people believe such figures are guaranteed the Advertising Standards Authority's ruling is an important step forward.

I worked in this area once, the road load model used did compare with real world conditions. This was derived from a run down curve from a steady state (ave of both ways on a level road)and replicated on the chassis dynamometer. Thus summing the wind res. Inertia and rolling resistance. We also replicated the std testing in the real world. However this was not as easy to repeat as accurately as on the dyno.

I have never had a car which has reached the 'official' figures but some have been much closer to them than others. It obviously depends on how you drive, the number of passengers, road conditions, congestion, length of journey etc etc. The laboratory conditions can never be replicated on the open road. However, it would help car buyers make a better informed choice of car if they could have some consumption figures that they actually had any faith in. It's hardly surprising that people who buy a car expecting it to do 60-70 mpg but achieve 42 are less then happy with the garage that sold them it. Anything which can help the long suffering motorist has got to be a good thing.

No account is taken for air resistance when measured in a laboratory.

I don't agree with S. M. most customers I speak to believe that the published figures are what they could expect from the car. I usually respond by saying that if you drive in the hills of Wales or in the flat country like Holland how can the figure be the same. There are many variables like how many passengers, weights and driving style. This will now make our job selling cars better.

The fuel consumption figures published by manufacturers are measured under test laboratory conditions, not on the road, to ensure comparability. They don't mean a thing in the real world and this should be emphasised more. Also beware the figures that are displayed by in-car computers, which can be as much as 10 percent optimistic, yet few people question them.

This is the same as the US "YMMV" guidance, isn't it? So it's hardly new.

I think most realise the figures are just for comparison only. But looking at the limited information about the actual test, I think that is where the problem lies. Do they do the town test at peak times or at midnight ? I suspect the driver only weighed bout 3 stone. In this day and age with all these flight simulators etc. I would have thought they would put it in a simulator that covers real traffic conditions of town, twisting country lanes, hills, motorways. just a driver [15+ stone] full car. Then you will get a real idea of consumption. Everyone drives differently so why not have test centers where there is a simulator that you can find your level of consumption. I think driving in such a simulator should be part of the driving test before drivers even get in a car and definitely before they drive out of the test area.

The mpg test should be carried out on a road/test track to at least try and simulate real conditions without ducts being blocked off with tape etc to reduce drag.

I have managed to exceed the published figures for a new Honda Jazz in our old one. So it can be done but you have to drive like an 'old'.

When do we ever get 20-30c,about 10 times a year. How about -2c or 4c.

Surely most people realise these figures should just be used for comparison purposes between different models? I don't know what all the fuss is about.