Back in the mists of time, I judged a car only by its racetrack performance and its ability to get me a date – acceleration and speed were at the top of my list. But in the past few years I’ve been on a different automotive quest, hunting for the car that can carry me the furthest on a single litre of fuel.
Yes, I’ve turned into a hyper-miler – one of those economy nerds who obsess over the fuel-flow meter instead of the speedometer. Efficiency testing may lack the rush of lapping a racetrack, but it has its own rewards – I have spent countless happy hours exploring the mysteries of hybrid drive systems, theorizing about stoichiometric efficiency (geeky, yes) and trying to hit the 100-mpg mark (the everyday driver’s equivalent of the four-minute mile).
Now it’s time to have a look at my findings. There are five main categories of powerplant available on the car market today – gasoline, diesel, hybrid, plug-in hybrid, and pure electric. I’ve driven them all for extended periods, and have come to some conclusions about what works, what doesn’t, and what the average consumer should buy.
First – a pure electric vehicle is the most fuel-efficient choice of all. Does that mean you should buy one? No. A conventional gasoline-powered vehicle is the least-efficient of the five choices. Does that mean you shouldn’t buy one? Not necessarily.
Here’s a breakdown of my results with each type of powerplant, and the pros and cons of each. Before we get started, bear in mind that true efficiency starts with choosing the smallest, lightest, most aerodynamic car that will do the job for you. For some drivers, that may mean a giant SUV. For others, it means a fuel-sipping subcompact – our missions vary.
My testing of pure electric vehicles quickly showed me that these are the most fuel-efficient vehicles on the road today. (With BMW’s subcompact Mini-E prototype, I easily got the equivalent of more than 125 mpg without altering my driving style.) This is due to the inherent efficiency of electric drive systems. According to the U.S. Department of Energy, electric vehicles convert up to 62 per cent of the energy loaded into them off the grid into actual power at the wheels. This is about three times as efficient as a gasoline-powered car, which wastes up to 83 per cent of the energy contained in its gasoline (among other things, the energy is lost to the friction of moving engine components, and in the form of heat that goes out the tailpipe). But the electric car’s efficiency comes with some deal-breaker limitations, which include high cost and reduced space (a battery is many times larger than a gas tank).
But the real killer is range limit: even the most capable electric cars can only go about 400 kilometres on a charge. And when you run out of fuel (electricity, in this case) you need to find a place to plug in (if you can) and a good book (a full charge may take many hours). Although I enjoyed my time in electric cars, I would not choose one as a primary vehicle, and I cannot recommend the pure electric, except to a small subset of consumers. Infrastructure improvements (read “charging stations on every corner”) and improved power storage systems (like lightweight ultra capacitors that can be charged in minutes) have the potential to render the battery obsolete and make the electric car an excellent mainstream choice. But they’re not here yet – so the most efficient car on the market remains a bit player.
With the exception of pure electrics, these are the most fuel-efficient vehicles you can buy. To understand why, let’s look at the Toyota Prius, a car that is virtually synonymous with the hybrid genre. On a series of extended tests with the mid-size Prius, I was able to do better than 55 mpg (5.5 litres/100 km) on the highway without trying hard – and when I worked at it, I could achieve more than 65 mpg (4.3 litres/100 km). There are two key factors behind this efficiency – an extremely well-engineered powertrain and excellent aerodynamics (that ant-eater shape gives the Prius extremely low drag).
Like other hybrids, the Prius uses a sophisticated system to store, deliver and recapture energy. The gas you put in the tank powers a gasoline engine that works in tandem with a large electric motor. The brakes act as generators, recapturing energy and pouring it back into a large battery located in the tail. It all works seamlessly and brilliantly, taking you down the road on minimal fuel. I have tested a long list of hybrids, including subcompacts, luxury sedans and SUVs. All were markedly more efficient than their non-hybrid counterparts. Unlike pure electrics, hybrids have no range limitations, and they use gasoline – the most readily available fuel in the world. The hybrid’s downsides include higher initial cost, reduced towing capacity, and a slight reduction in luggage space due to the large storage battery. But if you want a super-efficient vehicle that will let you go where you want, when you want, this is it.