25 MPG combined won’t win any fuel efficiency awards, but it’s a reasonable figure for the 2021 Mercedes-Benz C300 4matic Convertible. Let’s be honest, nobody buys this stylish drop-top for its thriftiness. This car is for those who want open-air enjoyment, a luxurious driving experience, and the prestige of the Mercedes-Benz brand. Fuel economy is a secondary concern to sun-drenched cruises.

City and highway performance

The EPA estimates 22 MPG in the city and 30 MPG on the highway. The city figure reflects stop-and-go traffic, where the C300’s 2.0L turbocharged four-cylinder engine works harder, and the 9-speed automatic transmission shifts frequently. The highway figure is better, reflecting the engine’s ability to settle into a more efficient cruise at higher speeds. These numbers are EPA estimates, but aggressive driving will lower them, and a more relaxed style can improve them.

Annual fuel cost

According to the EPA, the annual fuel cost for the 2021 Mercedes-Benz C300 4matic Convertible is $2,300. This figure is based on driving 15,000 miles per year, using a national average fuel price. Your actual fuel costs will vary depending on your driving habits, the type of fuel you use (premium is recommended), and local gas prices. While $2,300 might seem high compared to a hybrid, it’s the price for the luxury and open-top thrills this car offers.

Real-world expectations

The EPA numbers are a useful benchmark, but real-world fuel economy can differ. C300 Convertible owners often report figures slightly below the EPA estimates, particularly in combined driving. This is understandable, considering the type of driving this car encourages: weekend trips to the coast, spirited drives on winding roads, and idling while showing off. If you’re consistently achieving the EPA numbers, you’re probably not enjoying the C300 Convertible to its fullest potential. For an overview of C300 MPG across all years, refer to our model-specific guide.

How it compares

Competitors like the BMW 430i Convertible achieve a slightly better 28 MPG combined. Audi’s A5 Cabriolet Quattro manages 27 MPG combined, offering luxury and performance with a slight edge in fuel efficiency. Even the Lexus RC 300 Convertible gets an estimated 24 MPG combined, despite not being as luxurious or sporty. If fuel economy is a concern, other convertibles offer similar open-air experiences with better frugality. However, none quite match the prestige and overall driving experience of the C300.

Tips to maximize efficiency

Smooth and steady acceleration is best when trying to save fuel in the C300. Avoid sudden bursts of speed and hard braking. The 9-speed transmission is designed to optimize fuel economy, so let it do its job. The more you manually override it with aggressive driving, the faster the fuel gauge will drop.

Ensure your tires are properly inflated. Underinflated tires create more rolling resistance, which forces the engine to work harder and consumes more fuel. Check your tire pressure regularly and inflate them to the recommended pressure listed on the driver’s side doorjamb.

Consider using the vehicle’s “Eco” drive mode, if equipped. This mode adjusts the engine and transmission settings to prioritize fuel efficiency. While it might slightly reduce the car’s performance, it can make a difference in fuel consumption, especially during city driving.

Minimize idling whenever possible. Modern engines are efficient at restarting, so turning off the engine when stopped for more than a minute will save fuel. Extended idling wastes fuel.

Keep your vehicle properly maintained. Regular oil changes, air filter replacements, and tune-ups ensure that your engine is running efficiently. A poorly maintained engine will burn more fuel, negating any efforts you make at efficient driving. Compare this vehicle to all Mercedes Benz fuel economy data here on FuelEconomyHub.