A little PH experiment I would like your help with
Discussion
This is an MPG question so if that bores you switch off now.
Obviously where you get manufacturers MPG figures they often bear little relation to your own driving.
Where if find the biggest discrepancy for me is on the 'extra urban' cycle.
Our current family car is a Peugeot 5008 diesel which supposedly does 60 mpg+ extra urban.
WIth these low powered cars I find that above 70 the fuel economy gets horrendously worse. I'd be curious as to what all your cars do at a stead 70 mph, 80 mph and 90 mph.
So in my case against a 62mpg extra urban claim I get 46mpg at a steady 70, 41.5 at a steady 80 and 37 mpg at a steady 90 (measured over about 10 miles)
As an interesting aside, I tested this in my old 996 and the difference between 70 and 90 was only about 2-3 mpg (aerodynamics I assume)
So can we conclude that if you like to go a little faster than you are supposed to on motorways then it is pointless buying a small engine economical car? That's what I want to find out. (I realise Honest John has similar for general driving but I want to know specifically about motorway driving)
Obviously where you get manufacturers MPG figures they often bear little relation to your own driving.
Where if find the biggest discrepancy for me is on the 'extra urban' cycle.
Our current family car is a Peugeot 5008 diesel which supposedly does 60 mpg+ extra urban.
WIth these low powered cars I find that above 70 the fuel economy gets horrendously worse. I'd be curious as to what all your cars do at a stead 70 mph, 80 mph and 90 mph.
So in my case against a 62mpg extra urban claim I get 46mpg at a steady 70, 41.5 at a steady 80 and 37 mpg at a steady 90 (measured over about 10 miles)
As an interesting aside, I tested this in my old 996 and the difference between 70 and 90 was only about 2-3 mpg (aerodynamics I assume)
So can we conclude that if you like to go a little faster than you are supposed to on motorways then it is pointless buying a small engine economical car? That's what I want to find out. (I realise Honest John has similar for general driving but I want to know specifically about motorway driving)
Edited by blindswelledrat on Tuesday 3rd December 13:24
The NEDC extra-urban test has a max of 120kph, which you're only at for 10s, the average is about 63kph. So no, at a motorway cruise you won't get anything like extra-urban figures in an un-aerodynamic shape of vehicle, but other cars (with big engines, say) might do better than the test because of the steady cruising without acceleration and/or in a more appropriate gear.
Krikkit said:
The NEDC extra-urban test has a max of 120kph, which you're only at for 10s, the average is about 63kph. So no, at a motorway cruise you won't get anything like extra-urban figures in an un-aerodynamic shape of vehicle, but other cars (with big engines, say) might do better than the test because of the steady cruising without acceleration and/or in a more appropriate gear.
That's what I was wondering and hoping that an array of responses on this might clarify thisAs I understand it... The fuel consumption figures given out by the manufacturers are not supposed to be a guarantee of what you will get in normal use.
They use 3 different scenarios and all cars are tested in strict conformance to the rules for each scenario.
By testing the fuel consumption in this way you can then see what every car consumes under the same laboratory conditions.
It is meant as a comparison of all cars tested under the same conditions so the consumer knows that the results will relate from car to car accurately, it is NOT a true indication of the consumption you will achieve under 'normal' driving conditions.
They use 3 different scenarios and all cars are tested in strict conformance to the rules for each scenario.
By testing the fuel consumption in this way you can then see what every car consumes under the same laboratory conditions.
It is meant as a comparison of all cars tested under the same conditions so the consumer knows that the results will relate from car to car accurately, it is NOT a true indication of the consumption you will achieve under 'normal' driving conditions.
PoleDriver said:
It is meant as a comparison of all cars tested under the same conditions so the consumer knows that the results will relate from car to car accurately, it is NOT a true indication of the consumption you will achieve under 'normal' driving conditions.
And yet, if you were to test a customer car on a dyno at the correctly measured load over an NEDC, the combined figure from that test correlates pretty well with the majority of the figures that the customer base report back.The test isn't the problem.
PoleDriver said:
It is meant as a comparison of all cars tested under the same conditions so the consumer knows that the results will relate from car to car accurately, it is NOT a true indication of the consumption you will achieve under 'normal' driving conditions.
Yes exactly. I understand why my extra urban figures are so far out, but I wanted to try and find the most economical car for the type of driving I doblindswelledrat said:
So can we conclude that if you like to go a little faster than you are supposed to on motorways then it is pointless buying a small engine economical car?
Correct. You should buy an elderly-but-in-good-nick petrol barge and spend the difference on fuel. My ancient-but-oh-so-comfortable 528i does 35MPG at 70MPH and it's at least a million times nicer to be in than a small "economical" car, especially on the motorway.blindswelledrat said:
Krikkit said:
The NEDC extra-urban test has a max of 120kph, which you're only at for 10s, the average is about 63kph. So no, at a motorway cruise you won't get anything like extra-urban figures in an un-aerodynamic shape of vehicle, but other cars (with big engines, say) might do better than the test because of the steady cruising without acceleration and/or in a more appropriate gear.
That's what I was wondering and hoping that an array of responses on this might clarify thisExtra-urban driving
The EUDC (Extra Urban Driving Cycle), introduced by ECE R101 in 1990, has been designed to represent more aggressive, high speed driving modes. The maximum speed of the EUDC cycle is 120 km/h; low-powered vehicles are limited to 90 km/h.
After a 20 s stop - if equipped with manual gearbox, in the 1st gear with clutch disengaged - the car slowly accelerates to 70 km/h in 41 s (manual: 5 s, 9 s, 8 s and 13 s in the 1st, 2nd, 3rd and 4th gears, with additional 3 × 2 s for gear changes), cruises for 50 s (manual: in the 5th gear [sic]), decelerates to 50 km/h in 8 s (manual: 4 s in the 5th and 4 s in the 4th gear [sic]) and cruises for 69 s, then slowly accelerates to 70 km/h in 13 s .
At 201 s, the car cruises at 70 km/h for 50 s (manual: in the 5th gear), then slowly accelerates to 100 km/h in 35 s and cruises for 30 s (manual: in the 5th or 6th gear).
Finally, at 316 s the car slowly accelerates to 120 km/h in 20 s, cruises for 10 s, then slowly brakes to a full stop in 34 s (manual: in the 5th or 6th gear, lat 10 s with clutch disengaged), and idles for another 20 s (manual: in neutral).
Total duration is 400 s (6 minutes 40 s econds) and theoretical distance is 6956 meters, with an average speed of 62.6 km/h.
blindswelledrat said:
So in my case against a 62mpg extra urban claim I get 46mpg at a stead 70, 41.5 at a stead 80 and 37 mpg at a steady 90 (measured over about 10 miles)
As an interesting aside, I tested this in my old 996 and the difference between 70 and 90 was only about 2-3 mpg (aerodynamics I assume)
It is also going to be the power of the car vs the wind resistance too, I would imagine.As an interesting aside, I tested this in my old 996 and the difference between 70 and 90 was only about 2-3 mpg (aerodynamics I assume)
My BMW 330 achieves about 35 mpg between 70-80. At 90 that will drop to around 30-33. Around town, even when not accelerating the mpg is more like 25-30 even at constant 30 mph.
Only one figure for me, but I hope it helps:
BMW 320d SE 2007 163. Extra Urban claim: 62mpg. Steady 70mph: 62mpg on the on board computer, which is usually a few percent different from a fill up to fill up figure if, like some, you trust that more.
Measuring the Lotus is much harder as it can only be done between fill ups, which I rarely do in such a light car.
Regarding my BMW, like the OP I can't quite see how 62mpg is possible extra-urban, because that includes accelerating and moments at rest with the engine running. The two figures only match as above if I zero the mpg counter at the start of my 35 mile motorway commute, do a steady 70 and then take a reading at the end. I think the point is that the EU figures are done in a lab and don't relate to the real world, but they do provide a scientific benchmark so that models can be compared with other models, like 0-60 for example.
BMW 320d SE 2007 163. Extra Urban claim: 62mpg. Steady 70mph: 62mpg on the on board computer, which is usually a few percent different from a fill up to fill up figure if, like some, you trust that more.
Measuring the Lotus is much harder as it can only be done between fill ups, which I rarely do in such a light car.
Regarding my BMW, like the OP I can't quite see how 62mpg is possible extra-urban, because that includes accelerating and moments at rest with the engine running. The two figures only match as above if I zero the mpg counter at the start of my 35 mile motorway commute, do a steady 70 and then take a reading at the end. I think the point is that the EU figures are done in a lab and don't relate to the real world, but they do provide a scientific benchmark so that models can be compared with other models, like 0-60 for example.
RobM77 said:
Regarding my BMW, like the OP I can't quite see how 62mpg is possible extra-urban,
SOrry, one of us has missed the point a little there. I think of "extra urban" as being motorway driving?I am referring to motorway driving here if I have used the wrong terminology.
To clarify: Are you saying your 320 does 62 mpg at 70 mpg? Very impressive if so
Power/weight really makes a difference.
I have 2 1.9 VW TDI's, a 2002 Golf GTTDI (130bhp) and a 2007 Passat (105bhp)
The Golf gets between 48mpg at 100 and 54mpg at 60 (averages 52 everyday)
The Passat got 38mpg at 100 and 70mpg at 50 (averaged 44 everyday
I recently chipped the Passat to about 125bhp and its now 44mpg at 100 and 60mpg at 50.(average 52 everyday
I have 2 1.9 VW TDI's, a 2002 Golf GTTDI (130bhp) and a 2007 Passat (105bhp)
The Golf gets between 48mpg at 100 and 54mpg at 60 (averages 52 everyday)
The Passat got 38mpg at 100 and 70mpg at 50 (averaged 44 everyday
I recently chipped the Passat to about 125bhp and its now 44mpg at 100 and 60mpg at 50.(average 52 everyday
blindswelledrat said:
RobM77 said:
Regarding my BMW, like the OP I can't quite see how 62mpg is possible extra-urban,
SOrry, one of us has missed the point a little there. I think of "extra urban" as being motorway driving?I am referring to motorway driving here if I have used the wrong terminology.
To clarify: Are you saying your 320 does 62 mpg at 70 mpg? Very impressive if so
My understanding of 'extra urban' as far as official mpg figures go is that it's a mixture of driving in a non urban setting. The definition will be somewhere on the web, but I think it involves a bit of motorway, a bit of A road, some stop start etc. Generally it defines most of my driving around my local area, but I average about 48mpg for that. I don't think the EU figures allow for 1 lepton B road driving and frequent sideways action though
I find with extra urban you can get 2 extremes for mpg.
I've had as much as 74mpg over a 100mile trip back from when I had dpf delete and remap done on the motorway.
I'll often see 80+mpg on a nice straight 50/60mph road
Yet when I go on the motorway I'll see as low as 40mpg with average usually being around 54mpg.
All tests done with cruise and OBC reset for testing purposes.
With motorways being like a roller coaster though it's no wonder you don't get manufacturers claimed mpg plus the fact that conditions do not match lab tests as stated.
Maybe someone should do a youtube channel where they borrow cars on a runway for example and do mpg tests at different speeds so we the consumers can get an idea of mpg and those interested can see just how out real figures are. Although this test would still not be 100% accurate I rekon it would certainly be interesting
I've had as much as 74mpg over a 100mile trip back from when I had dpf delete and remap done on the motorway.
I'll often see 80+mpg on a nice straight 50/60mph road
Yet when I go on the motorway I'll see as low as 40mpg with average usually being around 54mpg.
All tests done with cruise and OBC reset for testing purposes.
With motorways being like a roller coaster though it's no wonder you don't get manufacturers claimed mpg plus the fact that conditions do not match lab tests as stated.
Maybe someone should do a youtube channel where they borrow cars on a runway for example and do mpg tests at different speeds so we the consumers can get an idea of mpg and those interested can see just how out real figures are. Although this test would still not be 100% accurate I rekon it would certainly be interesting
Edited by smiffy180 on Tuesday 3rd December 13:41
RobM77 said:
Measuring the Lotus is much harder as it can only be done between fill ups, which I rarely do in such a light car.
Get a bluetooth OBD reader. Then you can get your smartphone to show instantaneous and trip MPG as well as just about everything else the ECU is measuring. You can even tie it into the GPS on your phone to log MPG by location, speed, throttle position, or whatever else you want. They only cost about a fiver.
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