Want to use less fuel? The solution may be a button many drivers keep ignoring

Most modern cars have a start-stop system designed to reduce fuel use and emissions. The technology shuts the engine off when a vehicle stops at a traffic light or in a jam, then restarts it when the driver releases the brake or presses the clutch.

Its main advantage appears in city traffic, where vehicles spend more time stationary. Research cited in the article indicates fuel savings of 5% to 10% in such conditions, while an SAE study recorded savings of up to 26.4% in a simulation of extremely heavy traffic. On highways, where stops are infrequent, the effect is negligible.

The savings depend on other systems running in the car. Air conditioning on a hot day can sharply reduce the benefit because the vehicle computer restarts the engine more often. One test saw savings fall from 9.5% to 2.9% solely because the air conditioner was operating.

Cars with the system use reinforced components to withstand repeated starting. These include a stronger starter designed for up to 500,000 cycles, a more expensive AGM or EFB battery, and an electrical system that keeps the radio, ventilation and lights working while the engine is off. Some engines also use specially coated, low-friction bearings.

The system does not activate whenever conditions are unsuitable. The engine may need to reach operating temperature, while low battery voltage, extreme outside temperatures, full air-conditioning use and steep slopes can prevent shutdown. Many drivers still turn the feature off because of restart vibrations, a slight delay when moving and concerns about long-term component durability.