I think there needs to be some clarity in the law. It should be explicitly stated that the advertised fuel consumption figures reflect the appropriate standard test regime which is intended to simulate real world driving conditions. What else can a manufacturer do? How else can a consumer compare one vehicle against another, if all manufacturers don't submit to the same standardised test?
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I think there needs to be some clarity in the law. It should be explicitly stated that the advertised fuel consumption figures reflect the appropriate standard test regime which is intended to simulate real world driving conditions. What else can a manufacturer do? How else can a consumer compare one vehicle against another, if all manufacturers don't submit to the same standardised test?
The Federal Governments Green Vehicle Guide states that mandatory fuel economy figures are derived from laboratory tests, and that the purpose of the label is to provide a common basis to compare the efficiency of individual vehicle models.
No test can simulate all real world conditions.
Any attempt to try and do so would be a total waste of time as there are too many variables, the biggest flaw is the driver. Just observe next time you are driving how people accellerate when a traffic light turns green, likewise when approaching a red traffic light wether they get there fast and brake or start to slow down before, either needing little or no braking to stop.
We recently bought a 2013 5 door Suzuki Vitara with 78,000kms on the clock (genuine- never flat towed).
All the online sources give an average fuel consumtion of 9.5 L per 100.
We've now had 3 tanks of fuel through it & the average fuel consumption , both from the onboard computer & from our own calculations show that it's average consumption is dead on 9.5L per 100.
Not as frugal as some, but it is all wheel drive & a lot easier on the wallet than the 4.2TDi Patrol.
Not to forget that the manufacturers use for testing the most narrow tyres blown up to the maximum PSI, no accessories on the vehicle including footwell mats, mud flaps or footwell light globes.
Also the lowest spec model which is lighter. No payload other than a lightweight driver & fuel tank & other fluids at I believe 70% to save weight. Why most cas have a "biscuit" spare wheel & a full size spare as an optional extra to save weight.
So lab test standards are as useful as any vehicle review test not loaded to designed payload.
Can't actually recall when I was in the Kimberleys in an empty vehicle without at least 1 litre of emergency drinking water!
Australian standards & all vehicle reviews have less credibility than the typical council strip landmine!
If people even bother to waste the energy turning their head to look at the fuel efficiency sticker on the windscreen. They are better off putting their head through the windscreen & hope they cut their carotid artery going through the glass than withdrawal!
My car's official City Cycle is 13L/100km. Off peak traffic is actually 17L/100km & about 20L/100km peak traffic. But it's still worth the extremely quiet ride in my personalised acoustically modified car with compressor fridge 24/7.
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In my experience the car dashboard displayed fuel consumption in average litres per 100km is not accurate either. On all of our recent cars I have checked fuel use at the bowser vs kilometres travelled (over about 5 tankfuls) and found actual consumption is 1 to 2 litres higher per 100km than that which is consistently shown on the dashboard.
In my experience the car dashboard displayed fuel consumption in average litres per 100km is not accurate either. On all of our recent cars I have checked fuel use at the bowser vs kilometres travelled (over about 5 tankfuls) and found actual consumption is 1 to 2 litres higher per 100km than that which is consistently shown on the dashboard.
Rodsvan, the onboard computer system cannot recognize when car is driving as opposed to standing still or just idling on the driveway - the miles/kilometers travelled therefore cannot accurately be compared to fuel consumption.
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I see your point Possum3 however we live in a rural area and the nearest town doesn't have much traffic so in our normal driving the cars are never sitting and idling at traffic lights etc. I have also checked when travelling on long highway drives and they are also overly optimistic. Some of our cars have had the feature where the engine switches off at intersections, although it doesn't affect fuel consumption for us due to the type of driving we do.
I have read reviews of cars by motoring journalists where they have commented on the car dashboard display showing a lower than true fuel usage (although I can't confirm if they have spent any time in city traffic).
Rod
Our 2014 Honda CRV average consumption is very very close to actual fuel refill and km travelled, maybe .2 per 100 out, on both town and trip.
( A significant difference between the two though on actual consumption)
The cars we have had which have had significant differences were Pajero, VW Tiguan, VW Passat, Kia Carnival and BT50 (aka Ford Ranger) all diesels. Most have been around 1 litre per 100 difference. We had a hire car one time which was consistently almost 2 litres difference but I can't remember what it was (maybe a Suburu).
Our last VW changed the display to litres per hour when not moving. It showed a fuel use of 0.9 litres per hour when the car was at idle in the driveway. Thus it would have to be at idle for over 1 hour for every 100km to be the reason for the extra usage - probably easily possible in city traffic, but not for us (the car had engine stop/start anyway). And I never warm up engines before driving off, I just drive gently for 5 mins.
Variations on how much fuel goes in before the bowser clicks off could not be the culprit either - at 800km between refills it would have to be a difference of 8 litres each time. I averaged it over 5 tankfuls anyway. My assumption has been that manufacturers set them so that we think we're using less than we really are.
Rod
Where is the fuel flow sensor? Is there a photo of an automotive sensor anywhere?
If there is no sensor, I guess that the ECU could estimate the fuel flow by assuming that the fuel pressure is a known constant, and then referring to a lookup table which correlates fuel flow with injector pulse width.
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If there is no sensor, I guess that the ECU could estimate the fuel flow by assuming that the fuel pressure is a known constant, and then referring to a lookup table which correlates fuel flow with injector pulse width. That is basicly how it works on petrol vehicles, & its not 100% accurate. The reason fuel fuel flow sensors dont work, is theres a constant flow of of exess fuel from the pressure regulator back to the fuel tank.
The fuel flow is calculated from the following ; number of injectors and duration of opening pulse.
The fuel pressure is constant and the injectors are calibrated for delivery volume.
Also I doubt that the computer does not know if the vehicle is in motion as it has input from the speed sensor in order to calculate distance travelled.
This is calculated from number of pulses and tyre rolling circumference.
I have every single docket since the car was new in 2014. It started out as interest as the data was there. Stopped compiling the information but it is all there if I was bored to tears. On the back of each receipt I pencil in the car's data & zero the trip meter.
The numbers wander a touch but on average are the same.
Things like 99.9 L/100km sitting at traffic lights or 0.0 L/100km coasting down steep hills. But zeroing after each tank full/trip meter cycle, not a lot of difference.
Swings & roundabouts, but over the long term the same.
P.S. Average speed in Sydney traffic 28kph.
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Procrastination, mankind's greatest labour saving device!
50L custom fuel rack 6x20W 100/20mppt 4x26Ah gel 28L super insulated fridge TPMS 3 ARB compressors heatsink fan cooled 4L tank aftercooler Air/water OCD cleaning 4 stage car acoustic insulation.
