22 MPG combined won’t get the 2018 Mercedes-Benz S450 4matic any green car awards. But that number is almost irrelevant to the typical S-Class buyer. This is a vehicle purchased for its opulence, technology, and unshakeable road presence. Fuel economy is a distant consideration, almost an afterthought given the supreme comfort and prestige this flagship sedan delivers.

City and highway performance

The EPA estimates the S450 4matic at 18 MPG in the city and a more acceptable 28 MPG on the highway. That city figure reflects the reality of hauling a large, luxurious sedan through stop-and-go traffic. The 3.0L turbocharged six-cylinder engine, while smooth and powerful, needs a steady supply of premium fuel to deliver its 362 horsepower and all-wheel drive capability. On the open road, the nine-speed automatic transmission helps the S450 stretch a gallon further, but the aerodynamic profile of a large sedan can only do so much.

Annual fuel cost

According to the EPA, the annual fuel cost for the 2018 Mercedes-Benz S450 4matic is $2,650. This figure is calculated based on driving 15,000 miles per year with a specified percentage of those miles driven in the city versus on the highway, using the national average fuel price at the time of calculation. This estimate provides a standardized way to compare the fuel costs of different vehicles, but your actual costs may vary depending on your driving habits and local fuel prices.

Real-world expectations

While the EPA estimates provide a benchmark, real-world fuel economy for the S450 can vary significantly. Aggressive driving, frequent short trips, and even the use of all-wheel drive in normal conditions can all negatively impact fuel consumption. Conversely, careful highway driving at consistent speeds can potentially yield numbers closer to, or even slightly above, the EPA’s 28 MPG estimate. However, owners should realistically expect to see combined fuel economy in the high teens to low twenties in mixed driving scenarios.

Consider exploring S450 MPG across all years to see trends.

How it compares

The S450’s fuel economy sits roughly in line with its competitors, though nuances exist. The BMW 740i xDrive, with its turbocharged inline-six, offers similar performance and all-wheel drive, and posts an EPA combined rating of 24 MPG. The Audi A8, with its comparable 3.0T engine, also lands in the low-to-mid twenties for combined MPG. The S450 stands out because of its focus on sublime comfort. Buyers cross-shopping these vehicles are often willing to accept a slight fuel economy penalty for the S-Class’s unparalleled interior refinement and advanced technology features. If better fuel economy is desired (and the luxuriousness toned down), buyers could consider the Lexus LS 500h hybrid, which achieves a considerably better 28 MPG combined, albeit with a different driving experience. Remember to browse all Mercedes Benz fuel economy data for a broader view.

Tips to maximize efficiency

Maintain consistent tire pressure. The S450 is a heavy vehicle, and underinflated tires increase rolling resistance, forcing the engine to work harder and consume more fuel. Regularly check and adjust your tire pressure to the recommended levels listed on the driver’s side doorjamb.

Drive smoothly and avoid aggressive acceleration. The S450’s twin-turbocharged engine delivers ample power, but using it frequently and abruptly will significantly decrease fuel economy. Gentle acceleration and anticipation of traffic flow can make a noticeable difference.

Minimize idling. Letting the engine idle for extended periods wastes fuel. If you anticipate being stopped for more than a minute, it’s generally more efficient to turn off the engine and restart it when you’re ready to move again. The S450’s start/stop system helps with this, but being mindful of idle time will still add up.

Use cruise control on the highway. Maintaining a consistent speed on the highway minimizes unnecessary acceleration and deceleration, allowing the engine to operate more efficiently. Using cruise control can help improve fuel economy on longer trips.

Reduce unnecessary weight. Carrying extra weight in the trunk or cabin needlessly increases fuel consumption. Remove any items that are not essential to improve the S450’s efficiency.