23 MPG combined won’t win any fuel economy contests, but for the 2016 BMW 640i Convertible, it’s almost irrelevant. This isn’t a car for saving gas; it’s a symbol of success, a luxurious open-air ride powered by a smooth inline-six. Buyers want driving pleasure and prestige more than saving money on gas.

City and highway performance

The EPA estimates 20 MPG in the city and 30 MPG on the highway for the 640i Convertible. This reflects the car’s design and how it’s usually driven. The city MPG accounts for stop-and-go driving, where the turbocharged engine works to move the car’s weight. The highway MPG is better, showing the engine’s ability to cruise efficiently at speed, helped by the smooth 8-speed automatic transmission. This transmission is designed to keep the engine in its best power range, giving quick acceleration when needed while also saving gas during steady driving. Expect the 30 MPG to be accurate on long trips if you don’t speed. Go much faster than 75 mph, and that number will decrease.

Annual fuel cost

The EPA says the annual fuel cost for the 2016 BMW 640i Convertible is $2,500. This is based on driving 15,000 miles per year and using average national gas prices. What you pay will change, depending on how much you drive, how you drive, and local gas prices. The 640i needs premium fuel, which increases the annual cost compared to cars that use regular gas.

Real-world expectations

EPA numbers are a guide, and real-world MPG will change based on driving style, traffic, and even tire pressure and temperature. Drivers who accelerate quickly can expect MPG closer to the city estimates, while those who accelerate gently and drive at similar speeds might beat the highway estimate. The 640I MPG across all years is fairly consistent, suggesting that the engine’s design greatly affects fuel consumption. Expect to see a range of 18-28 MPG in mixed driving.

How it compares

The 640i Convertible is a specialized car, so comparing it to others requires thinking about what’s important to buyers. A Mercedes-Benz SL450 from the same year gets about 20 MPG city and 28 MPG highway, almost the same, but with a slightly different driving experience. The Audi S5 Cabriolet, with its supercharged V6, gets around 18 MPG city and 26 MPG highway. These small differences add up. A buyer who only cares about MPG might consider a Lexus RC 350, but that means giving up some luxury and the open-top experience. Buyers for a car like this generally aren’t also considering a Prius.

Tips to maximize efficiency

Use the car’s driving modes. “Eco Pro” mode helps save gas by changing how the throttle responds, when the transmission shifts, and how the climate control works. This mode works well for highway driving or stop-and-go traffic when you don’t need fast acceleration. Try it and see if the reduced responsiveness is acceptable for daily driving.

Keep your tires properly inflated. Check them often and keep them at the recommended pressure listed on the door. Underinflated tires increase rolling resistance, which reduces fuel economy. Checking with a tire pressure gauge can make a difference.

Remove unnecessary weight. Take out anything from the trunk that you don’t need. Extra weight increases the engine’s workload and reduces fuel efficiency. This is especially true in the city, where the engine is always accelerating and decelerating.

Drive smoothly. Avoid accelerating and braking hard. Look ahead and maintain a consistent speed when you can. Gentle use of the gas and brakes will improve fuel economy and the driving experience.

Follow the maintenance schedule. Regular oil changes, air filter replacements, and tune-ups keep the engine running efficiently. Follow the manufacturer’s schedule to keep the 640i running well. Those interested in all Bmw fuel economy data should consult other sources to confirm the best maintenance schedule.