Tony O'Kane | Dec 19, 2011 | 3 Comments


It’s a question that has hung around since the first-generation Prius arrived in showrooms in 1997 - do hybrids have a fuel-efficiency advantage on the highway?

Their urban-cycle credentials are well accepted. With fuel-saving features like engine start-stop and electric-only drive modes, most modern hybrids can achieve surprising fuel efficiency in even the heaviest traffic.

But take them away from the big smoke, and the picture is not so clear.

High-speed cruising takes the average parallel hybrid powertrain (a series hybrid, like the expected Holden Volt, is quite different) well out of its comfort zone.

At speeds above 70km/h, cars the like the Prius and Lexus CT 200h can’t operate under battery power alone, and the continuous running of the petrol engine at 100km/h diminishes the modern hybrid’s key advantage - the ability to run with its engine off to save fuel.

lexus ct 200h honda insight hybrid highway battle road test review 02c

Consequently, highway economy figures for parallel hybrids aren’t all too impressive, particularly when compared with the new crop of ultra-efficient diesels.

On factory fuel-efficiency claims, while a car like the Volkswagen Golf Bluemotion sips just 3.4 litres of diesel on the highway cycle, the Lexus CT 200h consumes 4.1 l/100km of petrol.

The outcome is reversed for urban commuting, with the Golf consuming 4.7 l/100km and the Lexus just 4.0 l/100km.

As noted, these are the raw claims quoted by the manufacturer and, as many will attest, they’re often at odds with what’s achievable in real world driving.

With that in mind, we took two hybrids out on the open road to find out exactly how they’d fare on Australian highways.

For this test, we chose an entry-level Honda Insight VTi and the mid-grade Lexus CT 200h F Sport.

Not only are the two cars separated on price (the Honda costs just $29,990, the Lexus $49,990), but they differ quite markedly on how their hybrid powertrains operate.

The Lexus employs the same system used by its corporate cousin, the Toyota Prius. At low speed and light throttle, it can propel itself for up to two kilometres under battery power alone, which saves a significant amount of fuel when crawling through peak-hour log-jams.

lexus ct 200h honda insight hybrid highway battle road test review 14

When the car is coasting or decelerating, the CT 200h’s 100kW 1.8 litre engine switches off to conserve even more fuel, and kinetic energy is recouped to recharge the on-board battery.

By contrast, the Insight seems a lot less sophisticated. Aside from when it’s at a complete stop with the brake pedal pressed, the Insight’s 72kW 1.3 litre engine runs almost constantly, the electric motor only cutting in when extra performance is required.

In the Honda, there’s no ability to drive under electric power alone, nor does the engine turn off when coasting. The Insight does have two key advantages though: light weight and a slippery shape - both of which should help it achieve good economy on the highway.

The Lexus weighs just under 1.5 tonnes, the Insight weighs in around 300kg less. The CT 200h’s heated leather seats, extra acoustic insulation and its bangin’ sound system will undoubtedly make long-distance cruising a pleasant experience, but the weight penalty incurred does no favours to fuel economy.

Our test route comprised a 650 kilometre loop through Eastern Victoria, running East from Melbourne along the M1, then along the A1 through Sale, Bairnsdale and Lakes Entrance before turning back.

lexus ct 200h honda insight hybrid highway battle road test review 15

This wasn’t a solid 110km/h cruise. There are numerous towns along the way with 80km/h and 60km/h speed zones.

We had no intention of hyper-miling either, so the air-conditioner in both cars stayed on and Eco mode remained switched off.

Remember: this was a real-world test, not an attempt to see if we could match the manufacturer’s claim. With that in mind, the results were very close between the two cars, and a little surprising.

We were far from hitting the quoted figures for the Lexus - claiming 4.1 l/100km - but we came within a hair’s breadth of achieving the Insight’s official 4.5 l/100km extra-urban consumption.

Our final 'real-world' numbers? The Lexus came home with 4.9 l/100km, closely bettered by the Honda at 4.6 l/100km.

The CT 200h’s engine, like the Insight’s, is almost constantly burning fuel at highway speed. The Lexus is also at a disadvantage due to its weight and less aero-friendly shape, but on the flipside, the extra luxury on offer makes it a very comfortable highway cruiser.

The Insight isn’t so comfortable and nowhere near as quiet inside as the Lexus. Yet we were pleasantly surprised by how close it came to its factory-quoted fuel economy figure, especially given the significant speed variations and hills encountered along the route.

That said, neither car would provide much of a challenge to a small-capacity turbo-diesel on the highway, but with each recording sub-5.0 l/100km fuel economy figures, you can’t exactly accuse them of being fuel guzzlers either.

More to the point, for cars that are arguably designed more for urban commuting, both the Insight and CT 200h did quite well on the open highway. Not perfect, but definitely not bad.


The Basics


Lexus CT 200h

  • Vehicle Style: Small hybrid five-door hatch
  • Price: $49,990 (plus on-roads)
  • Powertrain: 1.8 litre four-cylinder petrol engine and rear-mounted electric motor, producing a combined 100kW and 207Nm of torque.
  • Fuel consumption (claimed): 4.1 l/100km
  • Fuel consumption (tested here): 4.9 l/100km
  • Click here for full specifications.

Honda Insight

  • Vehicle Style: Small hybrid five-door hatch
  • Price: $29,990 (plus on-roads)
  • Powertrain: 1.3 litre four-cylinder petrol engine and electric motor, producing a combined 73kW and 167Nm of torque.
  • Fuel consumption (claimed): 4.5 l/100km
  • Fuel consumption (tested here): 4.6 l/100km
  • Click here for full specifications.
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