Does an automatic transmission car consume more fuel the slower it drives?
2 Answers
An automatic transmission car does indeed consume more fuel the slower it drives. Whether a car saves fuel or consumes more depends on road conditions, load, and speed. Driving slowly does not necessarily mean saving fuel, nor does driving fast necessarily mean consuming more fuel. It is related to the overall operating condition of the vehicle, such as high friction coefficients in some connections, overloaded weight, and the quality of the road conditions. Following the instructions in the car manual is the most fuel-efficient approach. Below is the classification method for car engine oil grades: 1. AB series: Oil for gasoline and light-duty diesel engines. 2. C series: Oil suitable for catalyst-equipped engines. 3. E series: Oil for heavy-duty diesel engines.
I believe driving too slowly indeed increases fuel consumption for automatic transmission vehicles, which I've deeply experienced through personal driving. Engines have an optimal operating range, typically between 1,500 to 2,500 RPM. When the speed drops below 30 km/h, the car often gets stuck in low gear—the engine revs high while the car moves slowly, leading to excessive fuel injection with incomplete combustion, wasting gasoline unnecessarily. During urban traffic jams when crawling at snail's pace, fuel consumption spikes noticeably. Conversely, smoothly accelerating beyond 60 km/h allows the transmission to shift up automatically, maintaining steady engine rotation and saving fuel. Over years of driving, I've found maintaining constant speed significantly more economical than frequent braking and accelerating, while also reducing carbon buildup. Keeping speed between 50-80 km/h is ideal—avoiding unnecessary slow cruising saves considerable fuel costs and environmental impact. Additionally, underinflated tires or excessive load also drag down fuel efficiency; regular checks of these details can optimize driving efficiency.
