For those of you wondering about "official" fuel economy...

[iriches]

Spotted a gem of a chart in a VW document on the web.  The full PDF can be found here, but the key chart is the one below:

 

Things to note:

1. Test is done at an ambient of 20 deg C, with all consumers switched off.  This is an unrealistic best-case-scenario.
2. The "urban" test is repeated 4 times, with the average fuel economy improving markedly after the first test and more slowly from then on as the engine warms up.  Thus if you are starting your car in sub-zero temperatures and only driving a few miles, with heater on full-blast along with lights, heated seats, mirrors, windows etc. you will see nothing like these figures!
3. The accelerations used are glacial.  As can be seen here, the first acceleration in the "extra-urban" part of the test sees the car go from 0-70 kph (0-44 mph) in 41 seconds.  Forty one.  When was the last time you accelerated so slowly?
4. Note that at the start of the "extra-urban" test the average fuel economy so far during the test only increases slightly. This means that the economy achieved during this acceleration will not be far off the 8.2l/100km (34 mpg UK) acheived in the urban test.  Put your maxidot in instant consumption mode and try to accelerate without it dipping below 30mpg!
5. The graph of speed against time is very straight-line-ish.  We tend not to drive like that. 

​This is why so many modern (especially turbocharged) cars fail to get anywhere close the the official figures.  At these mollusc-like accelerations the turbo is hardly being used, and so you get the benefits of the small capacity.  In the real-world, we work that turbo, and those benefits tend to disappear.... 

 

There is a new global test under discussion that should hopefully be a bit better.  Details can be seen here.  Note that:

1. The speed against time plot looks much more like real driving, with no absolute steady-state cruising
2. Maximum acceleration is now 1.6 m/s², against 1 m/s² in the current test cycle.  1.6 m/s² is equivalent to 0-60 mph in around 17 seconds (against 27 seconds in the old test). Still not exactly rocket-ship - but a bit more representative of real-world driving. 

Edited 23 February, 2015 by iriches

[Genoa1893]

Thanks for sharing.

[dieselV6]

The old test is indeed worthless, frankly the new one has been in the works for quite some time, but manufacturer's vested interests prevent any joint agreement. Put simply, manufacturers would have to present new cars with far worse set of numbers than the ones they replace - not good for sales.

 

But if the new test results somehow do make it into car brochures, I for one look forward to being able to look up fuel consumption above 80mph, as well as more realistic numbers for urban fuel economy.

[andyvee]

All manufacturers have to run the same test under lab conditions, it is not supposed to be indicative of real world driving, but give a level playing field so you can actually compare the figures.

 

http://www.dft.gov.uk/vca/fcb/the-fuel-consumption-testing-scheme.asp

[trundlenut]

Also the manufacturers are only allowed to provide the results of the official test, they are prevented by law from presenting any other figures.

This is part of the reason the ASA finding against Audi recently was a bit of a joke.

Sent from my Nexus 4 using Tapatalk

[JungleJames]

All manufacturers have to run the same test under lab conditions, it is not supposed to be indicative of real world driving, but give a level playing field so you can actually compare the figures.

 

http://www.dft.gov.uk/vca/fcb/the-fuel-consumption-testing-scheme.asp

Precisely.

I myself cannot see a problem. OK at times it may be annoying not being able to reach the stated figures, but at least you can fairly see which cars are the most efficient etc.

If anything, these real life MPG figures you see on some websites are the ones that don't mean anything. You have no idea how the cars have been driven or anything. You don't know if every set of figures that have been sent in have come from boy racers or whether they all came from the local womens institute. It could even be a fair mix, but you don't know that. Its quite possible for these websites to show figures that go totally against official figures. They may show engine A being more efficient that engine B, but the official figures show the opposite. Perhaps engine A had all grannys sending their figures in,, and engine B had all boy racers. Its entirely possible.

Official figures may be unobtainable, but at least they are fair tests.

[Sheldon.Cooper]

BUT the government uses the published figures to calculate the amount you can claim back when using a company car.  For a 2.0 diesel it's in the 1600-2000 bracket which is 53.25mpg (mean) and 45.3 (applied).  Because the farcical official figures are spiralling ever upwards you are lucky to hit the calculated figure and in the very near future it will cost you to drive your company car somewhere on business purposes.  My Octy manages 46mpg if I'm lucky but for shorter journies it's about 40.  The figure I can claim is based on 45.3 so on short journies it costs ME. 

 

So yes, there is a significant problem with these mpg tests.

[Dr_Pepper]

Thanks for the post and it all makes sense BUT

It doesn't explain why my mk1 and my mk2 both achieved their stated figures while my mk3 is so disappointing that it's the single thing which is going to put me off buying another one!

[iriches]

Thanks for the post and it all makes sense BUT

It doesn't explain why my mk1 and my mk2 both achieved their stated figures while my mk3 is so disappointing that it's the single thing which is going to put me off buying another one!

 

You'll be no better off with another brand/car.  All manufacturers are seeing NEDC official and real-world figures drift further apart.   The vehicle manufacturers in Europe have aggressive targets for CO₂ emissions that they have to meet or they will be fined.  These tests are the yardstick by which they are measured.  You cannot blame them for optimising heavily for these tests, which are clearly quite a long way from real-world driving.

 

If you're interested in seeing why the gap is growing in detail, there's a good report here.

Edited 24 February, 2015 by iriches

[Gerrycan]

Thanks for the post and it all makes sense BUT

It doesn't explain why my mk1 and my mk2 both achieved their stated figures while my mk3 is so disappointing that it's the single thing which is going to put me off buying another one!

 

 

Thanks for the post and it all makes sense BUT

It doesn't explain why my mk1 and my mk2 both achieved their stated figures while my mk3 is so disappointing that it's the single thing which is going to put me off buying another one!

I'm interested but more details please

• Current vehicle type, consumption for urban travelling and longer journeys (motorway)
• Has your typical type of journey changed between the first two and most recent vehicle
• Engine types in the first two vehicles

Cheers

[Geek42]

OK at times it may be annoying not being able to reach the stated figures, but at least you can fairly see which cars are the most efficient etc.

 

I'm not sure that you can. The fact that different cars have a different level of divergence from the official figures means that you're still guessing. The truth of the matter is that if you want to know for financial reasons then the amount of improvement is critical. If a particular car/engine costs £2k more to buy it's probably not the sensible economic choice if it's only better in fuel terms by a couple of mpg, so if the cheaper car achieves 90% of the official figure, and the pricier, more economic car only achieves 80% then it could still be more fuel efficient, but not by enough to pay the higher purchase price. I know it's not that straight forward anyway, when you consider residuals and tax/service costs etc. but the official figures don't give a fair comparison in my opinion.

 

It is true that the car manufacturers are only going down this route to optimise to government imposed targets, so you can't blame them, but the legislation is flawed. You've only got to look at the fact that hybrids are allowed to set the system in a state that uses battery power but doesn't replenish it to know that it can't possibly be a real average. Even with the minimal energy recuperation in the O3 a truly accurate 'average' figure would have to leave the battery state of charge in the same state that it started.

 

Yes, you have no idea who filled in the figures on sites like Honest John's, and if there was only one figure posted I wouldn't put too much faith in it, but if there's a large enough sample I think you have to believe that this figure will be much closer to reality than the official combined cycle (especially given that HJ quotes a range as well as an average). At least, that's what I believe anyway.

[JungleJames]

I'm not sure that you can. The fact that different cars have a different level of divergence from the official figures means that you're still guessing. The truth of the matter is that if you want to know for financial reasons then the amount of improvement is critical. If a particular car/engine costs £2k more to buy it's probably not the sensible economic choice if it's only better in fuel terms by a couple of mpg, so if the cheaper car achieves 90% of the official figure, and the pricier, more economic car only achieves 80% then it could still be more fuel efficient, but not by enough to pay the higher purchase price. I know it's not that straight forward anyway, when you consider residuals and tax/service costs etc. but the official figures don't give a fair comparison in my opinion.

 

It is true that the car manufacturers are only going down this route to optimise to government imposed targets, so you can't blame them, but the legislation is flawed. You've only got to look at the fact that hybrids are allowed to set the system in a state that uses battery power but doesn't replenish it to know that it can't possibly be a real average. Even with the minimal energy recuperation in the O3 a truly accurate 'average' figure would have to leave the battery state of charge in the same state that it started.

 

Yes, you have no idea who filled in the figures on sites like Honest John's, and if there was only one figure posted I wouldn't put too much faith in it, but if there's a large enough sample I think you have to believe that this figure will be much closer to reality than the official combined cycle (especially given that HJ quotes a range as well as an average). At least, that's what I believe anyway.

But what im saying is, on the whole, the difference between actual and official, if all cars were driven the same and in the same conditions, should be about the same. If one car achieves 90% of the official figures, then so should most of the others. If they don't, there is a good chance driving style or outside conditions have changed.

 

Also, despite being a rare thing, I reckon it should be possible to achieve the quoted figures at some stage or another. As I say, this will be very rare, but it has to be possible if everything is perfect. The overall average will never match the combined figure, but I reckon you could match it on one or two drives if you wanted.

Actually, just checked, the combined figures for the 2l diesel hatchback manual, are very achievable. I have matched them on at least one very long journey, which included a detour through rush hour Preston (well the outskirts anyway).

[Dr_Pepper]

I'm interested but more details please

• Current vehicle type, consumption for urban travelling and longer journeys (motorway)
• Has your typical type of journey changed between the first two and most recent vehicle
• Engine types in the first two vehicles

Cheers

Hi, yes to answer your questions the mk1 and mk2 were both 1.9tdi albeit different engines I understand, and the mk3 is the 2.0 184. No, my driving hasn't really changed and if anything I drive a lot more careful now, I was young when I had my mk1 and I drove like an idiot most of the time.

I abuse my diesels I only do about 6000 miles per year which is mainly 5-10 minute journeys plus a couple of long trips to Europe. But I used to do exactly the same 10 years ago and the mk1 gave me nearly 60 mpg come what may. I think the book figure was 58 mpg.

I obviously understand that I don't compare like for like with the new car, and i wouldn't for a second expect it to do 60 mpg, but to me that doesn't really excuse skoda for the huge gulf between their stated figures and the actual given

[Geek42]

But what im saying is, on the whole, the difference between actual and official, if all cars were driven the same and in the same conditions, should be about the same.

 

But I don't believe that's true. There are 'green' versions of cars out there that have official figures 5-10mpg better than the standard versions and in the real world get similar economy. There are lots of diesels that quote mpg in the 60's, in the 70's and sometimes in the 80's, and driven by me, in the same manner, I bet they would all get mid-high 50's. There are hybrid concept cars that claim 150mpg, but when driven by jourmalists don't get much better fuel economy than production cars.

 

There are plenty of models with two engines available where the smaller engine does great on the extra-urban element of the combined test, but due to the gearing the economy goes off a cliff above 50mph, so for motorway driving the bigger engine might actually better the economy of the smaller (or at least not do any worse). Now you might say, well that's because the smaller engine is designed more for a town runabout, but that's absolutely not apparent from the official figures, where the smaller engine wins on all counts by a healthy margin.

[Dempsek]

The BMW i8 is a good example of how bad the official figures are.

 

Official MPG 134.5 / 2.1/100 Km, real world driven by Auto Express 40MPG, Car and Driver (USA site) 30MPG.

 

Mind you the Telegraph did achieve 60MPG with careful driving and 40MPG in normal use. 

 

A real bargain at £100,000

 

As more and more hybrids hit the market able to run on battery power for more of the test the test will be less and less accurate.

[JungleJames]

Hi, yes to answer your questions the mk1 and mk2 were both 1.9tdi albeit different engines I understand, and the mk3 is the 2.0 184. No, my driving hasn't really changed and if anything I drive a lot more careful now, I was young when I had my mk1 and I drove like an idiot most of the time.

I abuse my diesels I only do about 6000 miles per year which is mainly 5-10 minute journeys plus a couple of long trips to Europe. But I used to do exactly the same 10 years ago and the mk1 gave me nearly 60 mpg come what may. I think the book figure was 58 mpg.

I obviously understand that I don't compare like for like with the new car, and i wouldn't for a second expect it to do 60 mpg, but to me that doesn't really excuse skoda for the huge gulf between their stated figures and the actual given

Well that's possibly an easy one to answer. Your Mk1 wouldn't have had a DPF. Your Mk3 definitely will do. However 5 to 10min journeys and 6000 miles per year probably means your car is attempting a forced regen as such, far too often, instead of relying on a passive regen. Hence your car will be burning a lot more fuel. The quoted official figures will not be taking regens into account. If you actually did longer commutes, youd possibly find your fuel economy would get a lot better.

[JungleJames]

But I don't believe that's true. There are 'green' versions of cars out there that have official figures 5-10mpg better than the standard versions and in the real world get similar economy. There are lots of diesels that quote mpg in the 60's, in the 70's and sometimes in the 80's, and driven by me, in the same manner, I bet they would all get mid-high 50's. There are hybrid concept cars that claim 150mpg, but when driven by jourmalists don't get much better fuel economy than production cars.

 

There are plenty of models with two engines available where the smaller engine does great on the extra-urban element of the combined test, but due to the gearing the economy goes off a cliff above 50mph, so for motorway driving the bigger engine might actually better the economy of the smaller (or at least not do any worse). Now you might say, well that's because the smaller engine is designed more for a town runabout, but that's absolutely not apparent from the official figures, where the smaller engine wins on all counts by a healthy margin.

1- I agree about hybrid. They screw the figures massively, and this is unfair. It catches people out. They need to have ahealth warning. No good except for short commutes to work where you never actually use the engine. I just ignore hybrid when it comes to these arguments, rightly or wrongly. If I remember rightly, I once saw figures for one hybrid, which clearly showed the extra urban figures worse than the urban figures. That should set peoples alarm bells ringing, but unfortunately it doesn't. I don't know what their individual figures all show now as I usually don't look at them.

 

2- Im not sure any of us are really 100% positive. I believe all cars (except hybrids) will show a similar difference when all driven the same in the same conditions, but you don't. Probably acase of agree to disagree. We would never prove it either way as it'll be virtually impossible to always have the same conditions. There is a good chance that when you believe you are driving the same, you actually aren't, or possibly the outside conditions are different.

 

3- Regarding the smaller v larger engine argument. The answer may lie in what speed the official testing uses for the extra urban figures. They are unlikely to use 70mph, so in real world driving the smaller engine will be a lot worse off. This I admit, will show a different percentage difference, and is something I should have made more obvious in my argument earlier.

 

 

I still believe the above shows the official figures are the most useful, in that they allow a fair comparison, although perhaps an extra figure on the side would be useful- A motorway speed figure.

Obviously what the figures should not be used for, as has been mentioned before, is for the government to work out monies owed for mileage based on the official figures. That is perhaps not what they should be used for, and not being a company car driver, I had no idea how this worked or anything (didn't even know you got rebates from government based on distance driven etc), so apologies if my argument annoyed any company car drivers etc.

Surely the official figures are handy for tax system though. I believe this is where it is good (well I suppose I would paying only £20 a year).

[Gerrycan]

Hi, yes to answer your questions the mk1 and mk2 were both 1.9tdi albeit different engines I understand, and the mk3 is the 2.0 184. No, my driving hasn't really changed and if anything I drive a lot more careful now, I was young when I had my mk1 and I drove like an idiot most of the time.

I abuse my diesels I only do about 6000 miles per year which is mainly 5-10 minute journeys plus a couple of long trips to Europe. But I used to do exactly the same 10 years ago and the mk1 gave me nearly 60 mpg come what may. I think the book figure was 58 mpg.

I obviously understand that I don't compare like for like with the new car, and i wouldn't for a second expect it to do 60 mpg, but to me that doesn't really excuse skoda for the huge gulf between their stated figures and the actual given

 

 

Others have already responded to your answer and I can only endorse that the 1.9D (PD) Octavia Mk2 that I had was a gem regarding economy.

When Skoda launched in Australia 7 years ago the 1.9d for some reason had very conservative fuel consumption figures, a combined of about 6.1l/100. Over 90,000km I think I only exceeded figure that on a tank on two occasions every other bettered it and most of that was due to the fact it has no PDF, so even multiple short journeys were no problem at all.

 

Much as I loved the diesel, when it came time to replace last year I knew that low annual mileage and mostly very short journeys similar to yours meant that a modern diesel with PDF was unviable. That and the diesel versions were substantially more expensive and a manual transmission unavailable made it a no brainer. 

The Aussie published fuel consumption figures for the 1.4tsi manual was 5.7l/100 but I knew that was probably optimistic and that is pretty much the case.

If my journey is less than 4km from cold (our summer so ambient is about 23 deg C) then consumption for the journey is going to be about 8l/100, but if it is about 10km then it improves to about 6l/100, unless it is very hot (40+C) and A/C runs all the time and adds 2l/100. Longer runs will give anything between 5.0 and 6.0l/100 depending on speed limits and how often the A/C cuts in.

In optimal urban runs where it is not too hot, I get a few green lights and maintain momentum I can get as good as 4.0l/100

Overall I am pleased with the petrol consumption and good figures are attainable but is a much greater challenge than the 1.9PD.

Oh, and the 1.4tsi is much faster accelerating and this is a temptation can not be wholly resisted.

Edited 25 February, 2015 by Gerrycan

[Sheldon.Cooper]

Thanks for the post and it all makes sense BUT

It doesn't explain why my mk1 and my mk2 both achieved their stated figures while my mk3 is so disappointing that it's the single thing which is going to put me off buying another one!

Yes it does, the government mpg tests when the mk1 and mk2 were around are different from todays tests.  They were a bit more realistic.

 

I've posted before that I've had 35ish cars and up until the Octy I was hitting 85% of the official figures, the Octy is 65%.

[jthyssen]

The problem is that a lot of car buyers think that the official figures = reality. Just to avoid that I would like them to change the official figures to something more realistic.

 

When my wife got a new car (Kia) there was actually a small leaflet explaining the difference between official figures and what to expect in real life -- the car dealer was probably tired of hearing complaints...

 

 

 

 

I have my Octavia as a company car on a 3 year lease. When I have to replace it I would actually consider a hybrid for the following reasons:

1) Company policies state petrol consumption must be 18.2km/L or better (51 mpg UK). This rules out Octy 2.0 TSI, Golf GTI and similar cars -- but includes Golf GTE

2) Cars in Denmark are outrageously expensive due to heavy taxing on the purchase, but hybrid cars get a huuuuuuge discount, so the Golf GTE is actually 20% cheaper than the Golf GTI -- and it is better equiped from factory. This is important both for tax reasons and as company policies has a specific limit for the purchase price.

3) I have a company petrol card (covers both business and private miles), so I don't care about the real-life consumption

[Yogi-Bear]

The BMW i8 is a good example of how bad the official figures are.

 

Official MPG 134.5 / 2.1/100 Km, real world driven by Auto Express 40MPG, Car and Driver (USA site) 30MPG.

 

Mind you the Telegraph did achieve 60MPG with careful driving and 40MPG in normal use. 

 

Look at the other side of the coin though - a stupendously quick and brilliant (by all accounts) supercar which does 30-40mpg (more if you drive carefully or can do short journeys on just the battery power) and doesn't have a massive RFL bill each year... I'd say that's not bad at all.

 

The i8 is a step in the right direction, and even higher up you've got McLaren and Porsche doing hybrid hypercars.  These are the first generation of such things, and will only get better.

[john96]

If it wasn't for the co2 emissions targets that the eu are forcing on the manufacturers, what engines would we be using and what mpg would we be getting? I suggest that without the dpf, egr etc, we would have more reliable and better performing engines.

[GTR27]

Others have already responded to your answer and I can only endorse that the 1.9D (PD) Octavia Mk2 that I had was a gem regarding economy.

When Skoda launched in Australia 7 years ago the 1.9d for some reason had very conservative fuel consumption figures, a combined of about 6.1l/100. Over 90,000km I think I only exceeded figure that on a tank on two occasions every other bettered it and most of that was due to the fact it has no PDF, so even multiple short journeys were no problem at all.

Much as I loved the diesel, when it came time to replace last year I knew that low annual mileage and mostly very short journeys similar to yours meant that a modern diesel with PDF was unviable. That and the diesel versions were substantially more expensive and a manual transmission unavailable made it a no brainer.

The Aussie published fuel consumption figures for the 1.4tsi manual was 5.7l/100 but I knew that was probably optimistic and that is pretty much the case.

If my journey is less than 4km from cold (our summer so ambient is about 23 deg C) then consumption for the journey is going to be about 8l/100, but if it is about 10km then it improves to about 6l/100, unless it is very hot (40+C) and A/C runs all the time and adds 2l/100. Longer runs will give anything between 5.0 and 6.0l/100 depending on speed limits and how often the A/C cuts in.

In optimal urban runs where it is not too hot, I get a few green lights and maintain momentum I can get as good as 4.0l/100

Overall I am pleased with the petrol consumption and good figures are attainable but is a much greater challenge than the 1.9PD.

Oh, and the 1.4tsi is much faster accelerating and this is a temptation can not be wholly resisted.

Sounds almost identical to my economy, almost the same car. We have ac on 100% of the time. Our average speed is low 30s and most trips are short. Our long term average (measured) is 7.5l/100. However, constant highway is mid 5s and any trip in town more than a few ks gets low to mid 6s. We don't drive that gently either. But short trips really kills economy! All our figures are with ac on. I'm surprised you don't seem to get much better, I would have thought it would have made more difference. For me, winter brings the best economy as we won't need ac, and temperatures drop to 10-25c which seems to be ideal for economy. This will be the first winter with the Octavia, so I'll report back when we get some figures!

[Richf]

1- I agree about hybrid. They screw the figures massively, and this is unfair. It catches people out. They need to have ahealth warning. No good except for short commutes to work where you never actually use the engine. I just ignore hybrid when it comes to these arguments, rightly or wrongly. If I remember rightly, I once saw figures for one hybrid, which clearly showed the extra urban figures worse than the urban figures. That should set peoples alarm bells ringing, but unfortunately it doesn't. I don't know what their individual figures all show now as I usually don't look at them.

Of course that will be the case , many hybrids run on 100% electric so around town the engine is rarely run making it the most efficient use of the car , hybrids are least efficient when bombing down the motorway at 70mph where they will be using fuel the entire time

[JungleJames]

Of course that will be the case , many hybrids run on 100% electric so around town the engine is rarely run making it the most efficient use of the car , hybrids are least efficient when bombing down the motorway at 70mph where they will be using fuel the entire time

Yep. Aware of that. Hence my comments. Hence why I mentioned about one hybrid actually making it obvious.

Unfortunately some people seemingly don't understand this, and wonder why they cant come close to figures given by hybrids.

Perhaps im far too anti hybrid, I don't know, but I would scrap the combined figure for hybrids, and base everything on the extra urban figure. Its unfair how such ungreen cars can be in such cheap tax brackets. Then greener cars are stuck in more expensive brackets.

 

Especially for company cars. If they are being purchased as company cars, then the chances are they will be bombing up and down the motorway most of the time, using an inefficient petrol engine, and getting rubbish MPG (especially if they are trying to charge the battery at the same time).

But they are in a really cheap tax bracket. A diesel will use a lot less fuel, and is more expensive. When working out this tax bracket for company cars, or whatever it is, governments should be ignoring the battery side of it, and look at the MPG/ CO2 output based on the engine being used the whole time.

Governments are hardly being green if they put hybrids in cheap company car tax brackets. They are being the opposite.