If you’re interested in buying a new car with a focus on fuel efficiency, you’ve probably noticed that most vehicles get better gas mileage on the highway than in the city. That makes sense; highway cruising usually requires less work than city driving. So, why do some hybrid cars get better fuel economy in the city than they do on the highway? Let us explain.
Fuel Economy Calculations
Before we cover the reason that hybrid vehicles get such excellent city fuel economy, it’s important to explain exactly how gas mileage is calculated. With today’s cars, three numbers make up a fuel economy rating: city mileage, highway mileage and combined mileage. The city rating primarily examines city driving patterns, factoring in stop-and-go traffic, low speeds and a small stint on the highway. Meanwhile, the highway rating consists of highway driving patterns, featuring primarily high-speed cruising with little stopping and starting.
The combined rating isn’t strictly a combination of the two. Rather, it’s an average that’s weighted a little more toward the city rating because most drivers spend more time in the city than on highways and rural roads.
Hybrid Cars and City Driving
Given that the city fuel economy ratings primarily involve low-speed and stop-and-go driving, it’s hard to imagine any car returning better gas mileage in the city than on the highway. But that’s exactly what happens with hybrids, largely thanks to a system called regenerative braking.
Regenerative braking is an energy-saving technology that hybrid vehicles have used since they first went on sale in the late 1990s. In essence, regenerative braking takes energy created during braking and harnesses it so the energy can be used for other purposes. In the case of many hybrid cars, this energy is sent back to the main battery, and that is used to power the car or extend the electric-only range, allowing the car to use less gasoline.
The result is that hybrid-car fuel efficiency actually improves when the car slows down. After all, the more stopping you do, the more electricity the hybrid can use to move the car forward. As a result, hybrid cars tend to offer slightly better gas mileage in the city because the low speed and increased braking mean more electricity and less gas are needed to power the car.
