Diesel-electric hybrid powertrains once appeared to have a bright future ahead of them courtesy of many carmakers including Toyota, which is now world-renowned for popularising series-parallel hybrid technology, but until now it has only offered this type of powertrain with petrol engines.
When asked whether Toyota is still investigating diesel-electric hybrid powertrains, Toyota chief engineer Keita Moritsu said the company is monitoring its potential.
“In the worldwide, diesel is of course a very important engine for LandCruiser,” said Moritsu-san.
Know the news with the 7NEWS app: Download today 
[In other markets, however] gasoline is the major technology… especially in America and China.
100s of new car deals are available through CarExpert right now. Get the experts on your side and score a great deal. Browse now.
“So that’s why we have arrived [at] our hybrid system with a gasoline engine.
“But in the future of course the situation in the worldwide is changing.
“So I need to monitor everything in the hybrid and electrification system.”
Toyota Australia manager of research, evaluation and training, Russel Tomlinson added that diesel-electric hybrid powertrains are possible, but they don’t provide as many benefits as petrol-electric hybrids.
“You need to respect the engineering challenge to make it practical and feasible,” said Mr Tomlinson.
“On a diesel engine you’ve got your low-end torque, whereas your electric motor would feed into a petrol. So that sort of complements the whole package.
“With diesel you’ve got low-end torque, [so hybrid assistance] might come on midstream and sort of support that through the drivetrain.
“But the difference versus and the engineering and effort to put it in is the challenge.”
Toyota Australia has previously said it’s looking at diesel-electric hybrids as part of its ‘multi-pathway’ solution to reduce CO2 emissions.
“We’re considering diesel hybrids, petrol hybrids… we’re looking at all forms of lowering the CO2 through multiple technologies,” said Toyota Australia head of product planning Rod Ferguson in 2021.
“There’s clearly differences… even in some parts of Australia whether you can access diesel or petrol. Different industries like to store fuels for other equipment that they use.
“So it’s not necessarily stating a preference for one over the other, but we’re open-minded to any of those pathways for electrifying.”
It’s worth noting that Toyota does have an electrified diesel powertrain, however, the ‘V-Active’ technology currently applied to its 2.8-litre four-cylinder turbo-diesel engine in the new Prado and certain HiLux variants is a 48-volt mild-hybrid system designed to reduce fuel consumption, and isn’t capable of driving vehicles under electric power alone.
Full-hybrid diesel-electric technology is far from unheard of in the car industry. Mercedes-Benz continues to offer diesel-electric plug-in hybrid (PHEV) powertrains in certain markets, but not Australia, and diesel-electric powertrains have long been widely used in heavy vehicles in the road, rail and marine industries.
In the local light vehicle sector, hybrid vehicles are currently experiencing a bigger surge in Australia than any other fuel type in terms of sales volume.
To the end of October this year there have been 144,071 new hybrid vehicles sold, accounting for 11.1 per cent of total vehicle sales. That means the popularity of hybrids is up 83.3 per cent compared to the same time last year.
Toyota dominates the hybrid vehicle market in Australia, where the Japanese brand sold almost half of all petrol-electric vehicles registered so far this year.
Earlier this year Toyota Australia announced it would axe all petrol-powered versions of its passenger models that already have a hybrid powertrain, including the Yaris, Corolla, Yaris Cross, Corolla Cross, and RAV4, among others.
In addition to its aforementioned V-Active mild-hybrid diesel engine, Toyota Australia also offers the petrol-electric i-Force Max V6 hybrid powertrain in the Tundra pickup locally, and says it is considering adding the 2.4-litre four-cylinder petrol-electric hybrid system that powers the new Prado in the US.
Toyota Australia continues to promise that all of its models will be available with a full-hybrid powertrain by 2030, excluding GR performance vehicles but including large off-roaders and commercials like the HiLux, Prado, LandCruiser and HiAce.