What type of powertrain is the most fuel- or energy-efficient? Is it battery-electric? Hybrid or plug-in hybrid? Gasoline or diesel?
Last week's second annual AJAC Eco-Run, from Ottawa to Montreal, provided some broad answers to those questions.
The purpose of the Eco-Run, organized by the Automobile Journalists Association of Canada (AJAC) was to demonstrate to consumers the broad range of automotive technologies currently available to help them reduce their fuel consumption and costs.
It was also intended to demonstrate that how you drive can be just as important as what you drive when it comes to saving fuel. The vehicles also ranged in size and type from sub-compact cars and compact SUVs to a full-size SUV and pickup truck.
There were different drivers in each vehicle for each of five different driving segments on the 250-km route, so direct car-to-car fuel-consumption comparisons were not possible.
It is possible however, to make note of several trends and key points.
First, and perhaps most important, when drivers apply
The overall average fuel-consumption for all 22 vehicles was just 5.27 L/100 km.
And most vehicles were able to equal or better the official fuel-consumption figures published in Natural Resources Canada's Energuide.
Fuel consumption typically tends to be greater in stop-and-go city driving than in highway operation, although there are some exceptions.
Vehicles with some form of electric drive or electrical supplement, tend to use less fuel/energy in city driving than on the highway.
Electric vehicles (EVs)
On a pure energy-efficiency basis, converting the electrical energy used to the equivalent energy contained in a litre of gasoline, EVs are significantly more efficient that other vehicle types in both city and highway operation.
But energy-consumption figures alone don't reflect the limitations of EVs in terms of limited range and long recharge times. While the gasoline- and diesel-fueled vehicles all completed the Eco-Run easily on a single tank of fuel, the EVs had to be recharged several times.
Plug-in hybrids, which can partially recharge their batteries by plugging into the electric grid, were the next-most-efficient as a group.
They achieved significantly better fuel economy than conventional hybrids in city driving, where they were able to operate in electric mode for much of the relatively short trips, but that advantage almost disappeared in longer highway operation.
Hybrids, as a group, had lower overall fuel consumption than gasoline or diesel vehicles, with their greatest advantage apparent in city driving.
When comparing vehicles of similar size and type, however, the best of the gasoline- and diesel-powered vehicles were as good as or better than some of the hybrids on the highway.
Advanced diesel engines
The diesel-powered vehicles tended to be slightly more fuel-efficient than their direct gasoline counterparts in highway operation, but not so in city operation.
The diesels used 28-percent more fuel per km in the city than on the highway, while the gasoline engines used 19-percent more.
Advanced gasoline engines
The best of today's advanced gasoline engines achieved highway fuel-economy results as good as or better than some of the hybrids, in comparable cars.
And, they achieved better fuel economy than comparable diesels in city operation.
There is no "one-size-fits-all" answer to which technology is the most fuel efficient. It depends on one's individual vehicle needs in terms of size, space and performance and on each person's predominant driving conditions and driving style.
When choosing a vehicle for your own needs, it is important to compare individual models as well as propulsion technologies to determine what suits best.
Twenty-two vehicles took part, showcasing a wide range of fuel-efficient technologies, including electric, hybrid and plug-in hybrid power as well as advanced gasoline and diesel engines. fuel-efficient driving techniques, as they did in this event, they can achieve some remarkably low fuel-consumption figures.