MPG the marketing swindle
Discussion
So I'm currently trying to find out how many mpg my car will make. 2000 model BMW M5. 5litre performace car of the sort the greenies hate, and done over 100000, so the government seems pretty keen to remove it from the road too.
Wife chose her new car very carefully as its MPG was important to her. She had to have room for kids/dog etc, so its a 2011 Nissan quashqi 2 litre diesel, with an astronomical and very green book figure of 54mpg.
Both I and my wife travel almost the same 16miles each way to work, with a fair amount of urban driving between peoples houses during the day.
Both cars have just been serviced. I reset both mpgs at the start of the month and we've both been trying to be economical.
In the last month my mpg as been 24.5, and hers has been 35.2. When you take into account the extra cost of diesel, the running figures get even closer.
Obviously, I'm always going to use more fuel than her, but it leads me to believe that the book figures for new cars have been totally massaged out of all proportion, and driving an old fuel thirsty car like mine is nowhere near double the pollution.
We even went back to nissan and said your car doesn't do anywhere near the 54mpg its advertised at and the guy literally shrugged his shoulders, saying no human could match the econocmy figures quoted as their done with machines!!!!!!
Wife chose her new car very carefully as its MPG was important to her. She had to have room for kids/dog etc, so its a 2011 Nissan quashqi 2 litre diesel, with an astronomical and very green book figure of 54mpg.
Both I and my wife travel almost the same 16miles each way to work, with a fair amount of urban driving between peoples houses during the day.
Both cars have just been serviced. I reset both mpgs at the start of the month and we've both been trying to be economical.
In the last month my mpg as been 24.5, and hers has been 35.2. When you take into account the extra cost of diesel, the running figures get even closer.
Obviously, I'm always going to use more fuel than her, but it leads me to believe that the book figures for new cars have been totally massaged out of all proportion, and driving an old fuel thirsty car like mine is nowhere near double the pollution.
We even went back to nissan and said your car doesn't do anywhere near the 54mpg its advertised at and the guy literally shrugged his shoulders, saying no human could match the econocmy figures quoted as their done with machines!!!!!!
I think the distortion between book figures and reality has been growing over the years.
I'm achieving a consistent 45mpg on a diesel Volvo which is probably not far from the book figures. However I've toyed with the idea of something like a Mini Cooper D until I discovered real world economy wasn't much better than i get for twice as much car.
I'm achieving a consistent 45mpg on a diesel Volvo which is probably not far from the book figures. However I've toyed with the idea of something like a Mini Cooper D until I discovered real world economy wasn't much better than i get for twice as much car.
You need to understand how mpg figures are generated and how even little changes in driving technique or roads can make a huge difference. My smart for example, I've personally had a low of 38mpg and a high of 67mpg. From the same car with the same driver. So it proves that I can affect the mpg by a huge percentage by just adjusting my driving stile and the types of journeys and roads I drive on.
I'm sure the claimed figures for most cars are attainable, but they are highly unlikely to be attainable under all driving conditions and by all drivers.
Also don't car makers quote 3 different mpg ratings? How close are you to any of them?
I'm sure the claimed figures for most cars are attainable, but they are highly unlikely to be attainable under all driving conditions and by all drivers.
Also don't car makers quote 3 different mpg ratings? How close are you to any of them?
I have no problem with the 'official' figures being done under controlled conditions that are identical for each manufacturer. If you want real world data it is easily available on the web from sites like www.fuelly.com or www.spritmonitor.de.
Lord 
said:
said: Similar to this, i have been pondering recently if Co2 output has any relation to mpg. I know its implied that a car with low Co2 if effiicant but in the real world is it?
I have no basis for comparision, only what i read on here. Its just been on my mind recently
They used to be totally related, as the MPG for the EU tests was calculated from the emissions. The reason being that with fuel injection systems it was very difficult to measure the fuel used as it's constantly being recirculated back to the tank.I have no basis for comparision, only what i read on here. Its just been on my mind recently
Apparently they now do actually measure the fuel - so you can get odd situations where one car will have better CO2 figures than another but worse MPG. But the difference is marginal and the Co2 figure is still a very close proxy for MPG.
I think the discrepancy is a bit of a scandal - in that some cars can get close, or even exceed, their stated MPG yet others are absolutely way out. So the whole "it's only a comparison" argument goes out of the window.
I bet another driver could get a lot more from the diesel. My wifes commute she gets about 43mpg from her 130 PD Golf, same 15m route I can get 10 more. There's a quite a lot of technique to eco driving & to mtach the drive cycle MPG calcs you need em.
Also a 16m commute I doubt either car will be up to temp (especially oil temps in winter) adding on 16m to the same commute & resetting the trip with it all warmed up I bet you'd see an average nearer to the book figure.
Also a 16m commute I doubt either car will be up to temp (especially oil temps in winter) adding on 16m to the same commute & resetting the trip with it all warmed up I bet you'd see an average nearer to the book figure.
Lord said:
said: Similar to this, i have been pondering recently if Co2 output has any relation to mpg. I know its implied that a car with low Co2 if effiicant but in the real world is it?
I have no basis for comparision, only what i read on here. Its just been on my mind recently
Very good point and one I haven't thought of either. I have no basis for comparision, only what i read on here. Its just been on my mind recently
I was reading the other day about a new hybrid Audi A5 2.0TFSi engine, with various electric motors and batteries so it produces a total of 316bhp.
Apparently it manages about 90mpg and puts out 80g/km co2
For the first 5 minutes maybe it does. Until the batteries are flat and you're running solely on the 2.0TFSi, in which case you'll get about 25mpg same as any other car.
The calculations for MPG need to be changed soon, as hybrids are 'cheating the system'.
Apparently it manages about 90mpg and puts out 80g/km co2
For the first 5 minutes maybe it does. Until the batteries are flat and you're running solely on the 2.0TFSi, in which case you'll get about 25mpg same as any other car.
The calculations for MPG need to be changed soon, as hybrids are 'cheating the system'.
Lord said:
said: I know its implied that a car with low Co2 if effiicant but in the real world is it?
^^ I noticed AutoExpress have started showing 'actual vs claimed' CO2 in their group tests.IIRC, BMW seems to be quite close to it's claims, but VAG products (Esp one that recirculate exhuast gases) seemed to be 40-50gm/km out against 'claimed'.
<Goes to find example he's thinking of>
Because my Mustang has 462hp and the torque of a gruntfuttocks wind breakage, it is far easier to maintain and hold average speeds and driven reasonably, it will return 30mpg - I've even seen 35 on the motorway. In general driven gently but still faster than your average family punt, it returns about 24.
The fallacy with CO2 is that it is based on per litre so a car's output depends on how much fuel it uses. Certainly my old Golf GTI will do 30-32mpg and the Mondeo 2.0 roughly the same but doing 3 times the mileage of the Mustang clearly both pump out more CO2. Given the Mustang is lucky to see 2000 miles a year, the total CO2 output is vastly less than an average Prius driven daily. Luckily for me, I only pay £210 a year and of late, only 6 months of that thanks to SORN because why should I pay for a zero emissions vehicle over the 6 months I don't use it? I could get my money's worth by burning a gallon in the garage every month though.
If there were any mileage in CO2, the Americans would doubtless have used it to drive people into smaller cars but I suspect there are certain things up with which they will not put.
The fallacy with CO2 is that it is based on per litre so a car's output depends on how much fuel it uses. Certainly my old Golf GTI will do 30-32mpg and the Mondeo 2.0 roughly the same but doing 3 times the mileage of the Mustang clearly both pump out more CO2. Given the Mustang is lucky to see 2000 miles a year, the total CO2 output is vastly less than an average Prius driven daily. Luckily for me, I only pay £210 a year and of late, only 6 months of that thanks to SORN because why should I pay for a zero emissions vehicle over the 6 months I don't use it? I could get my money's worth by burning a gallon in the garage every month though.
If there were any mileage in CO2, the Americans would doubtless have used it to drive people into smaller cars but I suspect there are certain things up with which they will not put.
cptsideways said:
I bet another driver could get a lot more from the diesel. My wifes commute she gets about 43mpg from her 130 PD Golf, same 15m route I can get 10 more. There's a quite a lot of technique to eco driving & to mtach the drive cycle MPG calcs you need em.
Also a 16m commute I doubt either car will be up to temp (especially oil temps in winter) adding on 16m to the same commute & resetting the trip with it all warmed up I bet you'd see an average nearer to the book figure.
if your car isn't warmed up after 16 miles there is something seriously wrong with it.Also a 16m commute I doubt either car will be up to temp (especially oil temps in winter) adding on 16m to the same commute & resetting the trip with it all warmed up I bet you'd see an average nearer to the book figure.
doogz said:
You're getting 24.5mpg from an M5, urban driving?
Have you calculated that yourself, or are you taking that from the car's trip computer?
Both, I calculated it in fuel but its only .1 mpg different to the clock.Have you calculated that yourself, or are you taking that from the car's trip computer?
My M5's always been good on fuel. On a purely motorway run between 60 and 70 in the slow lane it won't go below 30mpg.
If I reset the mpg and boot it on a road run however I get just below 20 mpg.
I think a lots also down to driving style. its not much fun driving the car at 24.5 (coasting to a stop, maximising fuel off over 1700rpm overrun etc). its quite a bit of fun driving at 23mpg (one or two full throttle accelerations and fairly normal eye on fuel consumption during the run) on the other hand 20 or below is almost certainly get yourself noticed by the plod type driving.
So for the enjoyment of the car 21-23 mpg is certainly the best compromise between enjoyment and fuel efficiency to my mind.
mnkiboy said:
I was reading the other day about a new hybrid Audi A5 2.0TFSi engine, with various electric motors and batteries so it produces a total of 316bhp.
Apparently it manages about 90mpg and puts out 80g/km co2
For the first 5 minutes maybe it does. Until the batteries are flat and you're running solely on the 2.0TFSi, in which case you'll get about 25mpg same as any other car.
The calculations for MPG need to be changed soon, as hybrids are 'cheating the system'.
Yes, the system seems to unfairly advantage plug-in hybrids, although I don't see a problem with 'normal' hybrids like the prius where all energy used to run the car comes from burning petrol.Apparently it manages about 90mpg and puts out 80g/km co2
For the first 5 minutes maybe it does. Until the batteries are flat and you're running solely on the 2.0TFSi, in which case you'll get about 25mpg same as any other car.
The calculations for MPG need to be changed soon, as hybrids are 'cheating the system'.
I cannot seem to find an example on the web but the manufacturer I work for has released a statement for us to give to customers explaining exactly how the MPG figure is worked out when they come in asking us why its not as good in real life as it is on paper,
basically it boils down to the fact that the figures are worked out in a lab on a test rig without the engine having any load on it what so ever, no power steering, air con, lights, heater blower, nothing, not even wind resistance.
You are never ever going to get close to those conditions, its silly but its an accepted practice, the only thing you can do is mentally wipe off at least 10 or so mpg off a quoted figure to reach the real world one.
basically it boils down to the fact that the figures are worked out in a lab on a test rig without the engine having any load on it what so ever, no power steering, air con, lights, heater blower, nothing, not even wind resistance.
You are never ever going to get close to those conditions, its silly but its an accepted practice, the only thing you can do is mentally wipe off at least 10 or so mpg off a quoted figure to reach the real world one.
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