Petrol or diesel? It has been a question that SUV buyers have been pondering for years. But now there’s a new form of propulsion to add to the mix: hybrid power.
We’re not talking about just any old petrol-electric system here. We’ve brought together the diesel-powered version of the Mitsubishi Outlander and pitched it up against its medium SUV body-double and our long-term loan car, the Outlander Plug-in Hybrid Electric Vehicle (PHEV).
The strengths of each SUV is clear. The diesel is bound to perform well on the highway, with the engine’s low-revving nature set to help it sip gently on its fuel of choice. The PHEV, on the other hand, should perform better around town, where its battery pack will be recharged as the regenerative braking system captures kinetic energy to feed back into its drivetrain.
For such a test, we decided to sample almost 50 kilometres worth of Sydney’s most congested urban roads, but only after 100km of motorway ring road driving. You can see a map of our route below.
Before we get to the drive, let’s sort out the key differences between these two otherwise identical mid-size softroaders – both tested here in their respective flagship Aspire specifications.
In the case of the diesel version, that means a price of $46,890 plus on-road costs, while the PHEV starts behind the eight ball, priced at $52,490 plus costs.
That’s a $5600 advantage to the oil-burner, which is enough for about 4000 litres of diesel, or more than four years of driving (if you average 15,000km per annum).
Aside from a few badges, these two vehicles look almost the same from the outside: in that respect the PHEV is something of an anomaly, as it is one of the most technologically advanced vehicles on the road, where many boundary-pushing vehicles opt for outlandish, aero-focused styling in the hope of a slightly better fuel use figure. If you look closely, though, you’ll notice a slightly different grille design and unique aero bits for the bumpers of the PHEV.
The petrol-electric model’s powertrain is cutting-edge, not to mention quite complex. The petrol engine is a 2.0-litre four-cylinder unit, which is teamed with pair of electric motors (one at the front axle and a second at the rear). The PHEV offers switchable all-wheel-drive, and comes with an automatic continuously-variable transmission (CVT) as standard.
The PHEV’s party trick is that it can be recharged by plugging it in to a power socket.
Mitsubishi claims it takes five hours to ‘fill’, but you need a 15-amp power outlet to charge it. The capacity of its battery is 12 kilowatt hours, so based on an average energy rate of $0.30 per kiloWatt hour (kWh) at peak times means a fill should cost $3.60, while off-peak charging is about half that amount. For the sake of this test, we charged at peak time.
The PHEV also allows you to recharge your batteries using the petrol engine, should it become depleted and you’re approaching a built-up area, where it will perform at its peak. The brand claims this will charge to approximately 80 per cent in about 40 minutes, while using about three litres of petrol (or costing about $4.20).
Where it grabs the eye of buyers is its fuel consumption claim of just 1.9 litres per 100 kilometres on the combined cycle.
The diesel can’t match that claim, with its 2.2-litre turbocharged four-cylinder unit claiming 6.2 litres per 100km – or nearly 70 per cent more than the PHEV.
It has 110kW of power (produced at 3500rpm) and 360Nm of torque (between 1500-2750rpm), with power sent to all four wheels via a switchable all-wheel-drive system and a standard six-speed automatic transmission.
In terms of their inherent practicality, the diesel gets the nod – it has seven seats, but because of the PHEV’s underfloor batteries, that car can only be had with five chairs.
However, both have similarly impressive boot space with five seats up (477 litres for the diesel and 463L for the PHEV), with that space increasing to 1608L with the second row folded flat.
The diesel’s seven-seat setup is handy, though the boot room is limited with all seats in use, with 128L of space – enough for a small suitcase or two, but no bikes or bulky camping gear.
All the extra powertrain stuff means the PHEV weighs 1810 kilograms – a full 200kg more than the diesel model. That’s no small impact, given the petrol engine has just 87kW and 186Nm at its disposal (the electric motor can boost that with 70kW more – provided the batteries are charged).
When the batteries are depleted, the little four-cylinder is working quite hard to pull its heft, and that weight also makes the ride of the PHEV more meddlesome than the diesel.
The PHEV’s wheels will jostle over smaller bumps and clang over larger lumps, and the diesel’s ride – while being far from perfect, and still exhibiting some front-axle thump – is much more comfortable.
Speaking of road manners, my co-tester Dan and I both thought the diesel would perform at its best on the open road, while the PHEV was expected to claw back some ground in the city. And that’s exactly what happened after we zeroed our trip meters and fuel use readouts before hitting the road from CarAdvice HQ in North Sydney.
We weren’t driving like hypermilers at that mythical ultimate fuel-saving speed of 77km/h – we kept to the speed limit and stuck to the left lane while semi trailers sped past on Sydney’s Hills M2 and then the Westlink M7.
Dan was dubious when the diesel he was driving was showing 5.7L/100km on the dashboard readout as we made our way away from town, as experience in diesel SUVs had suggested it would use closer to 4.0L in this situation. That readout was even higher than the claimed extra-urban use of 5.4L/100km.
Indeed, it seemed like the diesel’s dash readout was out of sync with the distance to empty function, which at one point stated 1000km till dry. And the displayed average fuel use figure didn’t dip away as we’d expected.
Unlike the diesel, the PHEV was showing a lower readout than expected on this leg.
Based on our previous highway experiences (where we were perhaps driving with a little more zeal) we had both expected a fuel use readout of about 7.0L/100km. Instead, the screen read in the low 6s – very close to the diesel’s readout.
What surprised us was the way the hybrid system kept switching to battery power, despite the fact I wanted the car to operate in Hold mode (where it supposedly saves its battery for the most opportune time and uses the petrol engine instead).
Still, it wasn’t too bad an outcome considering my readout was showing a lower average fuel use at the end of our freeway journey on the final ring road, the M5, where we stopped to stretch our (right) legs near the airport.
End of highway run - diesel readout: 5.7L/100km, PHEV readout: 6.3L/100km.
From here it was time to hit the grind of Sydney mid-afternoon traffic, where I expected the PHEV to gain back some ground – and so did Dan.
It is worth noting that at this point of the trip, the battery level was not at 100 per cent full, and while it has a claimed EV range of up to 52km – which would have got us back to the office with a couple of kilometres range to spare – the readout suggested only 32km of battery power.
That said, as we drove past Kingsford Smith airport and wound our way through the back streets of Sydney’s ultra-congested inner-west and south suburbs, the fuel use readout soon dipped below 6.0L … then 5.0L, then 4.0L, as the hybrid model relied upon its battery pack rather than its petrol engine for propulsion.
The diesel’s readout didn’t move far from its existing point, either, though it was a slow climb up from its winning highway trip computer figure. The turbocharged engine was relying upon its low-end torque to keep things moving, and while we were again keeping up with traffic, both Dan and myself were driving with a level of conservatism.
As I watched the battery range slip away in the PHEV, I was thankful for the fact the petrol engine was there as a backup for if – nay, when! – I ran out of electrojuice.
That happened about 36km in to the urban loop, when my fuel consumption readout had dipped to the 3s, which meant I would be calling upon the petrol engine to once again haul the PHEV’s mass for the majority of the time (it would still use battery power on occasion, once the regenerative brakes topped up the batteries enough to coast or accelerate slightly).
And so the digital display crept higher in both cars, as the demand on the diesel engine started to show the more time we spent driving – just in time for school zone hours.
Thankfully the traffic was relatively clear as we returned via the City West Link and the Harbour Bridge to company headquarters.
End of 150km run - diesel readout: 7.0L/100km, PHEV readout: 5.7L/100km.
So, it looked like a convincing win to the PHEV. Until we hit the fuel bowser.
Based on our actual refill figures, the PHEV used an average of 4.8L/100km over our 150km journey. The diesel, on the other hand, used only 5.7L/100km on average, so the trip computer claims in both proved pessimistic. The crucial bit was the diesel’s was even more pessimistic.
The PHEV used 7.66L of fuel and with petrol costing $1.569/L on the day we filled it ended up costing $12.02 to fill.
The diesel, over its 150km jaunt, cost $13.56 to fill, using 8.87L at a slightly lower $1.529/L.
That means to cover the same distance, the PHEV was $1.54 less expensive in terms of its bowser cost.
But the cost of starting with a full battery – based on that average peak charging cost – and full tank of fuel means it ended up being more expensive over our 150km run. Even with an off-peak charge, the difference would be negligible between the PHEV and the diesel.
Suffice to say, the diesel – with its better practicality, more enjoyable driving manners and significant cost advantage – proved the winner on the day.