20 MPG combined barely registers on the radar for most economy-minded car buyers, but those considering the 2021 Mercedes-Benz AMG C63 Convertible with its snarling 4.0L V8 often see it as a calculated compromise. This isn’t a car purchased for its frugality; it’s bought for its visceral performance, open-air thrills, and that unmistakable AMG exhaust note. It’s a weekend escape machine, a boulevard cruiser, and a statement of intent, efficiency is less important than exhilaration.

City and highway performance

The EPA estimates of 17 MPG in the city and 25 MPG on the highway reflect the C63 Convertible’s split personality well. In urban environments, the potent V8 and quick-shifting 9-speed automatic transmission are constantly engaged, leading to considerable fuel consumption. The stop-and-go traffic only exacerbates the issue, forcing the engine to work harder and negating any potential fuel savings. Out on the open road, the C63 Convertible can stretch its legs, benefitting from more efficient engine operation at cruising speeds.

25 MPG is still far from impressive, but it’s enough to make longer journeys bearable without constant refueling stops.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2021 Mercedes-Benz AMG C63 Convertible at $2,900. This figure is based on driving 15,000 miles per year, with a mix of city and highway driving, and using the national average fuel price at the time of calculation. It’s a considerable sum, certainly, but a realistic expectation for owners of a high-performance vehicle like this. Consider it the cost of admission for a driving experience few other cars can match. The $2,900 annual fuel cost may seem high when analyzing all Mercedes Benz fuel economy data, but it reflects this vehicles position as a high performance sports car.

Real-world expectations

While the EPA estimates provide a baseline, real-world fuel economy will inevitably vary considerably depending on driving style and conditions. Aggressive acceleration, frequent hard braking, and extended idling will all decrease fuel economy significantly. Owners can achieve figures closer to the EPA estimates, though surpassing them is unlikely, with more moderate driving and careful throttle control. Factors such as tire pressure, vehicle maintenance, and even weather conditions can have a subtle impact on fuel consumption.

How it compares

Compared to its rivals, the AMG C63 Convertible’s fuel economy is similar. The BMW M4 Convertible posts similar figures, around 17 MPG city and 25 MPG highway according to EPA estimates, and the Audi RS5 Cabriolet isn’t far off, with around 18 MPG city and 26 MPG highway. The Porsche 911 Cabriolet, specifically the Carrera S model, fares marginally better at around 18 MPG city and 24 MPG highway, but that comes with a significant price premium. For buyers prioritizing open-top performance and thrilling dynamics, these differences are often negligible.

The goal is finding the best blend of performance and luxury, fuel efficiency sometimes is near the bottom of the list after reviewing AMG MPG across all years.

Tips to maximize efficiency

Despite its performance focus, there are still ways to improve the C63 Convertible’s fuel economy. Smooth acceleration and consistent speeds are key. Treat the throttle with respect, avoiding sudden bursts of power unless absolutely necessary. This will minimize fuel consumption and prevent the engine from constantly dipping into the power band.

Ensure your tires are properly inflated. Underinflated tires increase rolling resistance, forcing the engine to work harder and therefore consuming more fuel. Regularly check your tire pressures and maintain them at the recommended levels, which are usually found on a sticker inside the driver’s side door jamb.

Minimize idling whenever possible. Letting the engine run while stationary consumes fuel without covering any distance. If you’re stopping for more than a minute or two, it’s best to switch off the engine. Modern engines start up quickly and efficiently, so there’s no longer any need to let them idle unnecessarily.

Take advantage of the car’s driving modes. The C63 Convertible typically offers various driving modes, including a Comfort or Eco mode. These modes prioritize fuel efficiency by altering the engine mapping, transmission shift points, and throttle response. They can help conserve fuel during everyday commutes and highway cruises, although they may not be ideal for spirited driving.