26 MPG combined is an acceptable fuel economy figure for the 2021 Mercedes-Benz C300 Convertible. It’s not especially thrifty, but it’s also not terrible for a small, luxurious convertible designed more for style and open-air enjoyment than outright efficiency. The C300 Convertible buyer is primarily focused on the experience, the prestige badge, the sleek lines, the wind in their hair, and understands that a certain level of fuel consumption comes with the territory.

City and highway performance

The C300 Convertible’s EPA ratings break down to 23 MPG in the city and 31 MPG on the highway. The city figure reflects the realities of stop-and-go driving, where the engine spends more time idling or accelerating from a standstill, neither of which favor less gas. The 31 MPG highway rating is more respectable, showing the benefits of the 9-speed automatic transmission and the 2.0-liter engine’s ability to cruise efficiently at higher speeds. The spread between city and highway suggests that drivers who primarily use the C300 Convertible for weekend getaways and scenic drives will likely see better overall fuel economy than those who mostly use it for commuting in congested urban areas.

Annual fuel cost

The EPA estimates that the annual fuel cost for the 2021 Mercedes-Benz C300 Convertible is $2,250. This figure is based on driving 15,000 miles per year and using national average fuel prices. Individual costs will vary depending on driving habits, local fuel prices, and the specific type of fuel used. The C300 Convertible requires premium fuel, adding to the overall expense of ownership. While $2,250 might seem high compared to more fuel-efficient vehicles, it’s a reasonable expectation for a luxury convertible with this level of performance and equipment.

Real-world expectations

Drivers can expect real-world fuel economy to change based on several factors. Aggressive acceleration, frequent hard braking, and carrying extra weight in the car will all negatively impact MPG. Conversely, smooth, consistent driving at moderate speeds, along with proper tire inflation and regular maintenance, can help drivers achieve figures closer to the EPA estimates. Keep in mind that putting the top down also affects efficiency by increasing drag, though most C300 Convertible owners aren’t likely to let that stop them.

How it compares

The C300 Convertible’s fuel economy is similar to other luxury convertibles in its class. The BMW 430i Convertible, for example, achieves a similar 28 MPG combined with its 2.0-liter turbocharged engine. The Audi A5 Convertible, with its 2.0-liter TFSI engine, is also rated around 27 MPG combined. These minor differences are unlikely to be a deciding factor for most convertible buyers. Those considering the C300 Convertible but prioritizing fuel efficiency above all else might want to look at more mainstream sedans or hatchbacks, or perhaps even explore the world of electric vehicles. See all Mercedes Benz fuel economy data for a specific overview.

Tips to maximize efficiency

Take advantage of the C300’s driving modes. The “Eco” mode optimizes the engine and transmission for fuel efficiency, softening throttle response and shifting gears earlier. While it may slightly diminish the sporty feel of the car, it can make a noticeable difference in MPG, especially on longer drives. Using cruise control on the highway also helps to maintain a consistent speed and avoid unnecessary acceleration, therefore saving fuel.

Ensure that your tires are properly inflated. Underinflated tires increase rolling resistance, forcing the engine to work harder and reducing fuel economy. Check your tire pressure regularly and inflate them to the recommended level found on the sticker inside the driver’s side doorjamb. Even a few PSI of difference can add up over time. Consider switching to low rolling resistance tires when it’s time for a new set.

Minimize idling. Idling consumes fuel without covering any distance. If you anticipate being stopped for more than a minute or two, turn off the engine. Modern cars are designed to restart quickly and efficiently, so there’s no need to let it run while you’re waiting. This is especially pertinent in city driving scenarios. Regular maintenance like replacing air filters also aids in efficiency. A clean air filter ensures optimal airflow to the engine, improving combustion and fuel economy. Refer to the maintenance schedule in your owner’s manual for recommended replacement intervals.

The 9-speed automatic transmission is designed to keep the engine in its most efficient RPM range. Avoid manually downshifting unless absolutely necessary, as this can increase fuel consumption. Letting the transmission do its job is generally the most fuel-efficient approach. Explore more C300 MPG across all years and body styles.