/ Motoring

How many miles can your car really do on a full tank?

Car fuel dial

Like many motorists you probably have a good idea of how many miles your car can do on a full tank of petrol. But do you know if it is anywhere near what the manufacturer claims?

When I bought my car, I wanted a reasonably priced vehicle, that was small and easy to park, and not too expensive to run. I chose a Peugeot 107, with an advertised 508 miles on a full tank of petrol. But after a few months I noticed I never managed to get near that – the closest I ever got was 330 miles.

Obviously I didn’t drive until the tank was completely empty so it could have done a few more miles, but that’s still quite a difference between the real and claimed figures.

New Which? research put 200 cars through the same test and found that 98% couldn’t match or beat their miles per gallon (mpg) claim. The car that performed worst compared to its official mpg figure was the Mitsubishi Outlander PHEV (a plug-in hybrid), which overstated its mpg by 120%, costing £459 a year in unexpected fuel costs.

Other studies have shown that the gap between official test results and how we drive in the real world has increased over the past years, so the problem could be getting worse. But why is this happening?

Why fuel claims aren’t accurate

The problem lies with the Europe-wide test used to measure fuel use, the New European Driving Cycle (NEDC).

The test is called ‘new’ but it was introduced in 1970 and last updated in 2007. It’s outdated and doesn’t properly measure the kind of driving we do today, for example on motorways.

It also contains a number of loopholes. Manufacturers can, for example, opt to switch off air con and lights when testing, or increase tyre pressure above recommended levels. And as there is no standard way of testing, this means that you can’t make a proper comparison between different cars.

Many of you have already told us you knew the claims were misleading. Malcom R told us in 2013: ‘EU fuel consumption figures do not represent real-life, and are not intended to.’ Vynor Hill said: ‘Manufacturers’ claims are of no use to anyone.’

It seems unfair that a product that isn’t meeting its claimed performance doesn’t suffer any consequences and consumers just have to bear the brunt of it, or do their own research.

Steering in the right direction

A new and improved fuel efficiency test that would address many of the current one’s weaknesses is due to be introduced in 2017 by the European Commission (EC). This actually closely mirrors our own test and more accurately estimates fuel use.

But some factions are trying to stall the introduction of the new test to delay it to 2020. That would be another five years of useless fuel claims.

We don’t think this is right, and are urging the EC to stick to the planned timing, so that you won’t be taken for a ride any longer.

Do you think official miles per gallon figures reflect reality? Do you agree the EC should bring in the new test by 2017?


I bought a new, manual, D5, Volvo XC70 in November, which was supposed to get a combined mpg figure of 53.1mpg. I didn’t expect to reach that, but did hope for the mid-to-high 40s as I do a fair amount of motorway driving. It is rare to get over 39mpg….I am really disappointed, as fuel economy was my second most important feature in choosing my car (safety of my children being the first), and the biggest reason I traded in my XC90 as it never achieved more than 29mpg. I’m surprised they didn’t make your chart for the wildly inaccurate figures.

When I bought my Golf 6 1.6 TDI I checked the mpg and found that the meter corresponded reasonably well with calculations made over a decent distance. Having checked again, the meter reads 57.8 mpg and my calculations for the last fill-up also produce a figure of 57.8 mpg. I cannot remember the official figures that the dishonest car salesman told me that I could expect.

Over the summer months I expect to average about 60 mpg. I am happy with these figures, remembering my first car struggled to average 30 mpg. OK, that was petrol, rather than diesel, but there is no doubt that modern cars are much more economical.

I want all manufacturers to stop taping up the doors, over-inflating the tyres, fiddling with the brakes etc. to produce artificially high figures. Take ordinary cars that have not been pre-prepared for the test. That could be done NOW, without waiting for a new test to be introduced.

It is important to bear in mind that the current test cycle has never been portrayed as representing real-life driving, and has become even less so as it ages, and vehicle technology has moved on. It was, and is, meant for comparative purposes only.

The laxity in the specification does allow values to be improved; however whilst we can complain about using them there impact is what is important, and that seems to be low. For example, not recharging the battery has, apparently, a 1% impact and lowering the tyre rolling resistance a 2%. I doubt, because of the speeds involved, that taping will have a substantial effect.

Who, perhaps, we should be criticising is the EU for not updating the NEDC at more regular intervals, and for framing a test standard in what seems to be a lax and, possibly, less than competent way.

The new proposed test standard seems to deal with these issues, but it will still be done under standardised conditions and is unlikely to totally reflect real life driving consumption (which will vary significantly of course from driver to driver). That is essential if testing is to be comparable from laboratory to laboratory. Let us hope that the EU do not persist in imposing unrealsitic targets and timescales which will hold up its implementation, as might be the case.

Malcolm – As a lecturer I could have prepared my students for their exams by telling them what questions would be on the paper, so that they could have focused their revision and achieved higher marks. That would have been utterly irresponsible and highly unprofessional.

Until the new tests are available, what is wrong with just testing cars without any preparation that would artificially improve their mpg figures?

Robert Harris says:
1 May 2015

The TV company I freelance with supplies a hired Jeep Cherokee in which I average 48mpg according to the dashboard display. I drive from home near Gloucester to Cardiff where I location-manage TV drama so have to use a car for scouting and organisation: 110+ miles per day along twisting A48, M4 and city streets. It’s a 9-speed auto diesel. An option to select ‘metric’ or ‘USA’ makes me wonder if the gallons in the displayed ‘mpg’ are USA or Imperial, but since USA gallons are smaller (1:0.83), imperial mpg would be even greater, so I suspect the mpg is configured for the UK market. I have an IAM advanced driving certificate and am HGV1, so I suspect my technique may be contributing to this performance.

Toyota 1.8 VVT-i HSD T Spirit 5dr 61 Registration. Official figure 74.3mpg

I bought this car on 18th September 2013. Having driven a Mazda 2 1.4L diesel for the previous 4 years which had averaged 63 mpg for most of its time with me (53mpg at point of selling) I was somewhat disappointed with this new car bearing in mind the mpg claimed for it and the superior technology it was deemed to contain. The Toyota garage I bought it from told me I did not understand how to get best performance from driving this hybrid. I was also told that driving with gradual acceleration was wrong – better to put my foot down, get up to speed and then use the better cruising facilities it offered. I still find this difficult to believe or prove. To be fair I have learned lots about getting good figures from it while driving in stop/start traffic and hilly, bendy country roads but am still bitterly disappointed with the overall figures as I have to drive on other roads too. As illustrated I had previously been able to get terrific figures from my Mazda 2 so I still
believe I know a little about driving fuel efficiently.

To date the average figures for mpg are:-

Range Average
Actual 40.2 to 52.6 48.5 (measured by filling up each time and comparing this with the miles covered)
Car’s computer 45.0 to 55.4 51.7
Difference 1.4 to 4.8 3.2

The quicker the new official figures can be made more appropriate the better. At present it is a complete lottery!

John says:
7 May 2015

I have owned a Toyota Yaris Hybrid (T Spirit model) from new in March 2013. My average fuel consumption, based on a driving mix of mainly local, some trunk roads and occasional motorway use is,according to the car’s on-board computer, 58 mpg. A far cry from the 85+ mpg claimed in Toyota advertising.
I note now with interest, the disclaimer statements that are routinely appearing in fine print at the foot of TV advertisements, that the mpg figures are obtained using a defined set of EU criteria, and the actual mpg achieved ‘will be affected by prevailing conditions etc etc’ – how true!!
Keep up the good work in pressuring the update of the NEDC driving cycle conditions to more accurately represent practical performance. A system of Accreditation for the laboratories utilised for such tests should also be mandatory.

I looked at the Hoda website, by way of example, and looking at the “Civic” “Range and Options” and picking one, it gave an mpg and CO2 figure with no warning they may not represent real life. So I emailed Honda to find out whether they should put this on their website. They came back to point to the “discover” tab on the same screen This does indeed give the caveat but I was then disturbed to see it suggested you would get from London to Paris and back on a tank, inferring the consumption would be as the EU figure. I was about to challenge them on this, but first looked on Honest John. The EU figure published was 78.5 mpg, the HJ figure was 67.1 = 88%. Overall Honda werer said to achieve 91% of real mpg. On this basis they seem to be doing very well, considering the inadequacies of the NEDC test, so I took it no further.

My only concern would be that I think anywhere an EU mpg is shown it should refer you to the unreality statement. We could do more to ensure people are not misled.

Sorry Honda! Not Hoda.

Paul Wilby says:
9 May 2015

Our car is a Sept 2014 Toyota Auris Hybrid. Now covered 6000mls.
We are careful drivers & expected to achieve around 58 to 60 mpg.
Reality is as low as 48 mpg in winter & 53mpg in spring & autumn.
Car readout is usually 4mpg higher, compared with fill ups & proper calculations.
We paid a good deal more for the hybrid, a big mistake it seems.

Emmanuelle wrote: “But some factions are trying to stall the introduction of the new test to delay it to 2020. That would be another five years of useless fuel claims.”

I would be very grateful if you could give us information about who is trying to hold up introduction of a new test.

According to ACEA on CO2 targets “Both the targets for 2015 and the targets for 2021 are the most stringent in the world. Accordingly, the 2021 targets for the European fleet are far tougher to achieve than those in the US, China or Japan (USA: 121g, Japan: 117g, China: 119g, bearing in mind that calculation methods vary in different parts of the world).”

There may be concern that meeting the EU target of 95g is making european cars less competitive in other parts of the world. Perhaps Which? could find out where the delay is and why. I had understood that quite apart from this the NEDC test would continue beyond 2017 in parallel with WLTP, and would not be superceded by the WLTP tests until 2020.

Kathryn Streatfield says:
10 May 2015

I bought a six month old Volvo V40 D2 in January this year. The claimed mpg for this car is 80 (combined).

Much of my driving is on the A1 as I have a 60 mile commute to work. Fuel economy is therefore important to me and I drive carefully. It is also one the main reasons I picked the V40 although I have long been aware of false mpg claims so did not expect to reach the claimed figure.

The V40 has a very useful trip statistics function which gives a detailed breakdown on fuel economy. The best I’ve done over a week’s driving is 68mpg and its more usual to do about 64.

This is still good, but way short of the claim. In fact it is only a bit better than the 2.0 Tdi Jetta I owned a few years ago (and that was a more powerful car).

I am disappointed in this aspect of the car – otherwise I’d say it’s a good car worth looking at.

My recent experience of hire cars is that mid-sixties mpg figures are readily obtainable from diesel engined cars driven sensibly on long journeys.

Hence I would agree that your Volvo is good but not extraordinarily so.

Kathryn, I’d be very happy to get 64 mpg on a weekly basis. It is testimony to the improvements that have been made in cars over the years. However there is clearly a problem with the perception many have of the “claimed” consumption. There has not been the right publicity, particularly from official sources, to explain that the EU tests that give these official figures are not representative of real life driving. These are not “claimed” figures – in the sense this is what you will achieve – they are figures produced from a laboratory-style test using a controlled driving cycle largely with the intention of putting emission figures on a comparative basis, and at the same time producing the asssociated fuel consumption again on a comparative basis. The results therefore are not claimed to represent real life and you need to look elsewhere for these. Carmagazine reviewed a V40 D2 4 cylinder and achieved 46mpg over 6 months.

Let’s hope this is made clearer, rather than allowing the misconception to be fostered that all the car manufacturers are willfully misleading us. Whilst there are criticisms of the use manufacturers can make of the laxity in the standard, if they choose to, the root cause of the discrepancies between “real life” and “official” seems to be down to an outdated standard that should have been amended and updated by the EU before now. Unless anyone knows differently 🙂

Manipulating numbers to make your case stronger seems to also extend to Which? Re-reading their report in the May magazine raised my eyebrows. The table of “Fuel economy phonies” list their worst vehicles. Now I would normally look at a “real life” mpg against a “claimed” (EU Official) mpg, or other comparisons of this type, by calculating how close it was to meeting the claim. So, if the claim was 148, and it achieved 67.3, I’d say it was 45% of the claim 67.3/148×100%). But not here – because Which? take the numerical difference,148-67.3, and then divides that by the achieved – 67.3 – to give 120%.

Now I don’t think it is necessary to play this numerical game, because 45% makes the point. I just don’t like the sly use of statistics – let’s leave that to the politicians.

I agree 110% Malcolm. 🙂

I had intended to send an email to Which? about this after I read the article. Here is advice on how to compare numbers: http://web.augsburg.edu/~schield/MiloPapers/984OfSigCompare3.pdf

I don’t think it was a good idea to focus on hybrid vehicles, where the figures are going to depend to a great extent on how the vehicle is used. The large discrepancies in fuel economy figures are shown perfectly well for petrol and diesel vehicles.

I have a Citroen C3 2003 with 113000 Miles, claimed mpg 64. I usually get about 55.
Recently I went to Popham airfield from Tunbridge Wells and back I checked mpg for this trip it returned 70 Mpg two up much to my surprise.
I suspect it was helped by road works nearly the length of the M3 with 50 restriction and speed cameras.

Rodney, you are getting nearly 10% more than the “claimed” EU mpg then. Perhaps the fuel companies should be taking the manufacturers to court for depriving them of 10% of their income. Please drive less carefully in future. If we all did what you do we might see an industry in real trouble. 😀

I have an 2007-2012 Hyundai i30. It averages ~35 mpg, against the manufacturer figure of 46.3 mpg. It’s especially bad at motorway speeds – it uses nearly as muchpetrol as my 3.5 litre Merc! Which? describes it as ‘worth a look’. It definitely isn’t.

Alex says:
29 June 2015

Hello Emmanuelle,

I found this article http://www.automotive-hub.blogspot.com that seems to expand further about what you are saying.
It is very surprising of the loop holes involved with the NEDC, not only does it result in inaccurate results in MPG, but it seems that manufacturers are given the opportunity to fiddle the results to some extent.

Here is a link to a recent RAC report about the efforts of Eurpoean car manufacturers to delay the introduction of the WLTP tests: http://www.raccars.co.uk/news/article/3305/european-car-makers-delaying-real-world-mgp-tests

Like other articles, this refers to how manufacturers cheat the NEDC tests by modifying vehicles prior to testing. What I would like to know is whether manufacturers will still be able to modify vehicles in WLTP tests.

C Brown says:
17 July 2015

I was disappointed by your article on this topic because it failed to register the real issue about tests and plug-in hybrids, which is that your actual MPG will depend entirely on how you use the vehicle. It is entirely possible to drive a plug-in hybrid and achieve infinite MPG. Your article suggested that ‘your fuel bill would be more than double’. Not if you drove the car entirely on its battery it wouldn’t.

What is needed is a new test for plug-ins which tells you what you really want to know. The current test is meaningless. For the record, my Mitsubishi PHEV has now done 2500 miles on around £60 of petrol, but I rarely drive more than 25 miles in it before recharging.

Lance says:
23 July 2015

We leased a 2014 Golf GTD – the salesman claimed a ‘easy’ 63mpg. When we first received the car, we barely made 43mpg. Over the last year, it has slowly increased to a maximum of 48mpg. This is a far cry from the 63 claimed by the Volkswagen marketing.

When I asked a VW sales representative what mpg I could expect from the car I was interested in he quoted the official test figures – which I was already familiar with. I questioned whether I could achieve such good fuel economy. He checked the figures on his iPad and recited them again, without any qualification that they may not be attainable.

Incidentally, the Advertising Standards Authority took the Volkswagen Group to task for misleading advertising in 2013: https://www.asa.org.uk/Rulings/Adjudications/2013/3/Volkswagen-Group-UK-Ltd/SHP_ADJ_210019.aspx#.VbDupHi4lE4

Jon Harris says:
25 July 2015

I ran a Seat Ibiza FR with a 1.9TDi for a couple of years and 20k miles and averaged high 50s, more if you were a little more sympathetic.Assuming the GTD is the more modern 16v 2 litre engine i imagine with a mixed route and sensible right foot 60+ would be on the cards.

Honest John’s “real life” mpg for the 2.0 GTD is 47.4 (aggregate of owners’ reports) so similar to your consumption. As comments above show this discrepancy is down to the EU test deficiency – yieldinhg the only figure VW must publish. However the salesman should know this is not a “real life” figure and has misled you. If you have evidence (a witness?) that he made this mpg claim you would have a case against the supplying dealer. An earlier contributor was successful doing this.

dewicymro says:
24 July 2015

I have a 2012 Toyota iQ. The manufacturer claims it will deliver over 65mpg. Reality is that , even driving quite gently, it is unusual for me to achieve better than 54mpg. I bought the car because of its claimed economy and really wish I hadn’t as the economy just isn’t there! Most of my driving is long distance and I rarely exceed 65mph. I think that the test should be modified to reflect reality so that consumers can make properly informed choices. I also drive a BMW Z4; this car achieves 35mpg against a manufacturers claim of about 33mpg.

It should be made obligatory that all car dealers should explain in full to prospective customers the “real world” figures, or perhaps more appropriately, produce a comprehensive written report to include all of the divergence and/or disparities that can affect mpg upon the sale of any vehicle such as those already described above which may add approximately 30% to a vehicles fuel consumption and that the extent of any variance more or less depends upon the owner/driver of the vehicle.

Jon Harris says:
25 July 2015

Perhaps i could suggest some wording?

“Please note that the standardised economy figures quoted are achieved are under, controlled repeatable conditions to enable you to make a comparison between different manufacturers products. Naturally the type of journeys undertaken and the way in which the vehicle is driven will have a significant impact on the economy achieved. Additionally, the very fact that we have to explain this to you causes us some considerable concern and we would respectfully suggest you refrain from driving until you have at least a basic understanding of how to drive a motor vehicle.”