By Paul Clarke
Model/Engine size: Mitsubishi Outlander GX4hs 2.0 PHEV Auto
Fuel: Petrol-Electric Plug-in Hybrid
Fuel economy combined: 156.9 mpg
The Mitsubishi Outlander PHEV (Plug-in Hybrid Electric Vehicle) – a two-tonne 4×4 with a two-litre petrol engine – has an official economy figure of 156.9mpg – how is this calculated and can you expect to achieve this in real-life?
This report – which was scheduled many weeks ago for release today – may be seen as good or bad timing depending on who is looking at it – as it comes on the day that it has been revealed that Mitsubishi has been calculating fuel economy incorrectly for a longer period – 25 years – than announced in news released a week earlier in April 2016. Currently this fuel economy testing issue relates to just four city car models sold in Japan, two of which were built for Nissan, and it has been said that UK vehicles are not affected.
Japanese fuel economy regulations changed in 1991 to require testing methods to better reflect stop-and-go urban driving, but Mitsubishi Motors didn’t follow that rule change. Mitsubishi has said it compiled data for fuel economy tests using U.S. standards, where higher-speed, highway driving is common, rather than Japanese standards, where more city driving usually consumes more fuel.
Mitsubishi said last week it had overstated fuel efficiency by up to 10 per cent on the four types of small cars sold in Japan, covering more than 600,000 vehicles.
Despite this issue so far affecting only four city cars sold in Japan, it has relevance to our report, as the Mitsubishi Outlander PHEV has an official economy figure of 156.9mpg, yet if you drive the Outlander on the motorway for any distance it’s likely that it will return somewhere between 30 and 35mpg.
This discrepancy – we hope – isn’t due to any falsification of test figures by the manufacturer, but instead is the result of the New European Driving Cycle (NEDC) fuel economy test. So why does the test produce a combined economy figure for the Outlander of 156mpg, yet if you drive the Outlander 10,000 miles per year on motorways you’ll come nowhere close to this figure?
It’s widely acknowledged that the NEDC test for petrol and diesel cars bears little resemblance to real-life driving, with our real-life economy figures often 20-25% worse than the official figures. However this variation is much worse with plug-in hybrids in typical driving.
The NEDC test – first introduced in the 1970s and not updated since 1997 – is conducted over a short distance, acceleration is gentle, and the test takes place on a rolling road in a laboratory. With increasing pressure to reduce emissions and improve fuel economy, engineers in car companies around the world have been faced with a challenge: to develop cars that perform well on the NEDC test.
Engineering cars that are optimised for the NEDC cycle has been the result, and this trend has been taken to new extremes with the advent of the plug-in hybrid. Such a powertrain is designed to perform extremely well on the NEDC test – dipping under the 50g/km CO2 barrier, and delivering around 150mpg – or more. The battery capacity is key to all this. To achieve the figures above, the battery needs to deliver around 30 miles of range.
The current NEDC test for conventional internal combustion engine vehicles has two parts: an urban and an extra urban cycle.
The urban driving cycle is repeated four consecutive times. The total duration is 13 minutes over a theoretical distance of around 2.5 miles, with an average speed of just over 11 mph.
The extra urban driving cycle has a total duration of 6 minutes 40 seconds with a theoretical distance of just under 4.5 miles, with an average speed of just under 40 mph.
The combined fuel economy is calculated by a total consumption of urban and extra-urban cycles over the total distance (theoretically just under 7 miles). The total test time amounts to just under 20 minutes with an average speed of just over 20mph. This obviously doesn’t reflect modern motorway driving speeds (where aerodynamics play a key part, as a vehicle’s drag increases by a factor of four as its speed doubles).
Plug-in hybrids – and range-extended vehicles – have a different variation of the NEDC test. The vehicle is tested under two conditions. Condition A is electric power; plug-in hybrid cars can start this test with a full battery and the energy used to charge the battery (usually from fossil fuels) isn’t taken into account. Condition B is with the battery depleted; it measures the distance achieved under NEDC test conditions on liquid fuel alone. The figures are then averaged out over a test cycle of the battery range (officially 32.5 miles in the case of the Outlander PHEV) plus 16 miles (so 48.5 miles in total).
The result of all this is that plug-in hybrids such as the Outlander have an official fuel economy figure that is based on a significant portion of the driving distance being carried out on electric power, and the energy used to charge the battery isn’t taken into account. So if you drive the Outlander PHEV short distances, primarily on electric power, then you may come close to the official 156 mpg NEDC economy figure. If you drive the Outlander on longer, faster journeys, primarily on the petrol engine, then you’re likely to experience a miles per gallon figure somewhere in the mid-30’s. And anywhere between the two mpg figures is possible depending upon a sliding scale of driving patterns.
After 16 weeks our average fuel economy from the Outlander PHEV is 56.4mpg. This has dropped from the previous 59.9mpg figure, primarily because we’ve been living a nomadic life for recent weeks due to builders moving in to our house, resulting in us losing access to a charge point. But we would still argue that 56.4mpg is excellent for a large 4×4, and there are none of the particulates and very few of the NOx emissions of diesels.
A new global harmonised driving cycle, the World Light Test Procedure (WLTP), is currently being developed, but it’s not due to be introduced in the imminent future, so for the moment we’re stuck with the prospect of the next economy/emissions scandal coming from the direction of the real-life economy of plug-in hybrids compared to the official NEDC figure.
Perhaps most significantly, in the light of recent revelations about emissions and economy figures from Volkswagen and now Mitsubishi, currently the manufacturers conduct the tests themselves, rather than an independent body doing this – surely this will now have to change?
So where does all this leave Mitsubishi? Well, it’s a real shame. If you’ve read our previous reports about the Outlander, you’ll know that we’ve rated it extremely highly. If you buy an Outlander PHEV based on the knowledge that to get the best out of the car you need to carry out most journeys on electric power, with occasional longer journeys on petrol power, then it’s a great car to drive, it’s a hugely practical workhorse, and it’s likely to be producing few of the tailpipe emissions that have such an adverse impact on local air quality and people’s health. Like us, if you also have access to a diesel car for longer journeys, then the Outlander really can make sense. The Outlander has also been a massive sales success for Mitsubishi.
The question is, if the recent news about Mitsubishi has the devastating financial impact that many commentators predict (the company has lost half its market value – almost $4 billion – since it admitted to manipulating test data) will the company scale back research and development of ‘conventional’ vehicles, or will it have no choice but to cut back investment into low emission technologies such as plug-in hybrids? The intelligent decision would be to go forward focusing on vehicle technologies that promise to lower emissions and improve fuel economy – in real-world driving.
Of course one of the benefits of reduced fuel consumption is saving money, and on that note, our next report looks at the potential financial benefits of driving a Mitsubishi Outlander PHEV.
For more information about the NEDC fuel economy test see:
Real-life economy: 56.4mpg after 16 weeks
NEDC electric driving range: 32.5 miles
Real-life electric driving range: 20 miles after 16 weeks
Official CO2 emissions: 42 g/km
Green rating: VED band A (£0)
Weight: 1,845 kg
Company car tax liability (2015/16): 5%
Price: £35,999 (after the current UK government Plug-in Car Grant of £5,000).
Insurance group: 22E
Power: 200 bhp
Max speed: 106 mph
0-62mph: 11.0 seconds
Torque: 385 Nm