Real-world MPG: Tow car fuel economy

Whether you are towing a caravan, boat or horsebox, all that extra weight and wind resistance hike your fuel bill significantly. Some cars are more adversely affected than others, though, which is why, at this year’s Towcar Awards, we gave six cars the full What Car? True MPG treatment.

All of the cars were chosen because of their impressive claimed Government mpg figures (albeit achieved with nothing in tow), or for their combination of a powerful engine and excellent economy.
Of the four conventionally powered cars here, the Renault Captur dCi 90 has the best claimed Government combined mpg figure of 76.4mpg. With the same engine and gearbox, the Dacia Logan MCV 1.5 dCi 90 posts a claimed 74.3mpg. Other contenders aren’t far behind; the Honda Civic Tourer 1.6 iDTEC has a claimed average of 72.4mpg and the Volvo S60 D4 Geartronic is claimed to achieve 67.3mpg.

Arguably, the cars with the most to prove are the two plug-in hybrids on test here. The way the official Government mpg figures are achieved means that the Mitsubishi Outlander PHEV and Volvo V60 Plug-In Hybrid have sky-high economy figures (148mpg for the Outlander PHEV and 155.2mpg for the V60). Each is also claimed to do slightly more than 30 miles on pure electric power, but how long do the batteries last when towing a caravan? Does economy nosedive once the batteries have been drained?

How the tests were done
Unlike car manufacturers’ laboratory tests, What Car?’s True MPG programme measures cars’ fuel economy on normal roads in everyday driving conditions, using state-of-the-art equipment attached to the car’s tailpipe. The six cars here were tested during this year’s Towcar Awards, with each car hitched to a trailer or caravan.

Dacia Logan MCV 1.5 dCi 90 Lauréate
Let’s start with the lightest and cheapest of our six cars, the Dacia Logan MCV. With a list price of just £10,795, the Dacia is something of a bargain, even in range-topping Lauréate spec. It also promises rock-bottom running costs, not least because of its remarkable claimed Government combined mpg figure. With a low kerbweight of just 1165kg (including 75kg for the driver not included in Dacia’s published kerbweight) and a legal towing limit of 1150kg, the Logan is better suited to pulling lightweight trailers. We matched it to one loaded up to weigh 800kg.

Driving away from our base at the MIRA test track and out on to the A5, the Logan pulled up to speed well despite the extra weight of the trailer. A downchange from fifth gear to fourth was needed on inclines, but the engine’s 162lb ft of pulling power meant it didn’t feel laboured. Then we hit the M42. The Dacia sat quite happily at 60mph in fifth and felt stable and settled. The return leg on the A444 incorporated several changes of speed limit, which showed the need for patience when accelerating, but there was no need to thrash the engine.

The result? The Dacia returned 34.3mpg when towing, an impressive benchmark for the others to beat.

Renault Captur 1.5 dCi 90 Dynamique Media Nav
With the same engine as the Dacia, the Renault was likely to run it close. Although it’s a little heavier than the Dacia (1245kg including 75kg for the driver), its low towing limit of just 900kg means the Renault can’t legally pull most caravans. So, like the Dacia, the Renault completed the route towing an 800kg trailer.

Unsurprisingly, the Captur’s performance felt similar to the Dacia’s. Acceleration was steady but there was no need to bury the throttle just to keep up with traffic along the A5 and out along the M42.
At a steady 60mph the Captur felt secure – if anything, more so than the Logan. Having returned to MIRA, we crunched the numbers and found that the Captur came up just short of the Logan MCV’s recorded towing economy, returning 33.8mpg.

Honda Civic Tourer 1.6 iDTEC EX Plus
The Honda may be the third-lightest car on the shortlist, but
its higher kerbweight (1412kg including 75kg for the driver) and legal towing limit (1400kg) mean it can legally be matched to small caravans. So, the Honda pulled a caravan weighted to 85% of the kerbweight (that’s generally accepted as a sensible maximum ratio for secure and stress-free towing).

The Honda drove along the A5 towing 400kg more than the Dacia or Renault, but then it had 221lb ft of pulling power to call upon, a big increase on the lighter cars’ 162lb ft. As long as the revs weren’t allowed to drop much below 1500rpm the Civic’s 1.6-litre engine pulled strongly enough.
At 40-50mph on the A5 the Civic felt reasonably stable, but once up to 60mph on the motorway it needed more steering corrections than the Logan MCV or Captur. The driver had to pay attention to sudden gusts of wind or when overtaking an HGV. This was less of an issue on the A-road section, but noticeable nonetheless.

The instant readout showed the Civic to be a little behind the two smaller and lighter cars – as you’d expect when it was towing something heavier with a wider frontal area. The Honda returned 28.9mpg.

Volvo S60 D4 Drive-E SE Lux Geartronic
The Volvo was included in our tests because of the promise of excellent fuel economy with prodigious power. As with Honda, the Volvo pulled a caravan weighted to 85% of the car’s kerbweight. The Volvo’s extra muscle was immediately noticeable as it effortlessly pulled up to speed. At a steady 50mph on the A5, the Volvo’s engine felt utterly unstressed, and the gearbox grabbed a lower gear smoothly when required.

Once driving on the motorway, the Volvo was secure and stable, and felt less fazed when overtaking lorries than the Honda. Accelerating back up to speed having passed through villages on the A444 was swift and easy, with no need to work the engine hard. Once the True MPG data had been analysed, the Volvo returned 30.1mpg.

Mitsubishi Outlander PHEV GX4hs
The lighter of the two plug-in hybrids on test, the Mitsubishi Outlander PHEV’s on-paper economy is miles better than any of the conventionally powered cars’. However, the New European Drive Cycle (NEDC) test regime does play to a plug-in hybrid’s strengths. We were intrigued to see what the Mitsubishi would do once we’d added a 1500kg caravan (the heaviest the Outlander PHEV can legally tow) into the mix.

Our first test started with a fully charged battery. With the petrol engine and both electric motors in use, the PHEV accelerated well; however, the 2.0-litre petrol was noisy at times. Although the performance was impressive, towing ate up the battery’s charge: we were less than halfway around our route when the battery was drained. Regenerative braking did top up the battery a little, but from now on, the PHEV mostly relied on its 2.0-litre petrol engine, and the weaker punch was noticeable.

Even so, at the end of the first circuit the Outlander had achieved a True MPG figure of 40.6mpg. Most caravanners drive a lot more than 20-odd miles to reach their destination, though, so the second test was begun with the battery drained. Although less responsive, the PHEV still towed well enough and kept up with traffic on the second run. We then checked the numbers and found that the Outlander had returned 24.7mpg.

Volvo V60 Plug-In Hybrid D6 AWD Geartronic SE Lux Nav
The heaviest car on our six-strong car shortlist has the best official economy figure: 155.2mpg. Would the V60 Plug-in Hybrid be able to match the Mitsubishi and achieve more than 40mpg towing with a fully charged battery?

Despite pulling a caravan weighing 1726kg (more than 200kg heavier than the Outlander’s), the Volvo was noticeably quicker from the moment we hit the A5. The Volvo felt more stable than the Mitsubishi, too, the firmer suspension allowing less movement. To start with, the Volvo’s electric motor did the lion’s share of the work, with the battery reduced to a minimum after 20 miles. Even without the extra punch of electric power, the Volvo still pulled strongly, with no need to rev the engine hard to maintain speed. Once the data had been analysed, the Volvo achieved 44.9mpg, beating the Mitsubishi by more than 4mpg despite towing a heavier caravan. 

On the second circuit with the hybrid battery now drained, the Volvo was able to recharge itself to some extent using regenerative braking, but for the most part the 2.4-litre diesel engine worked alone. Even so, the V60 achieved 29.6mpg, only 0.5mpg worse than the S60 achieved towing a much lighter caravan.

To see the full results of the Tow Car Awards 2014, click here.