"Intake-valve throttling has merits, but it isn't the only way to get the job done," said Ron Pierik, G.M.'s senior staff engineer for advanced engine technologies.
Cleaner engine technologies are on the rise.
It also said significant improvements could be made using inexpensive new engine technologies inexpensive.
Fast-moving advancements in conventional engine technologies, however, could change that perception.
Analysts praised Toyota's ability to keep increasing profits even while it invested heavily in new environmentally friendly engine technologies like hybrids and fuel cells, which run on hydrogen.
According to the industry-led International Air Transport Association, new design and engine technologies have decreased C02 emissions per passenger kilometre by more than 70% since the 1960s.
Given the high cost of developing engine technologies like turbocharging and direct fuel injection, working to improve tires can deliver worthwhile improvements for relatively small investments.
They are taking advantage of the new engine technologies to design planes that could cut into the sales of 737s and A320s over the next few years.
While some engine technologies quickly become industry standards, intake-valve throttling, which has been used on production automobiles for about 10 years, remains a relative rarity.
There's a strategy now between what many constructors are doing with new engine technologies, downsizing of the cars, emissions, the electric car.
Indeed, the technology costs of converting one form of hydrocarbon to another and the costs of providing alternative automotive engine technologies are also likely to fall.
