The latest EPA regulators have apparently gone light on the throttle while testing the new 2024 BMW 540i xDrive. The results are in, and the newest vehicle sporting the B58 engine offers remarkable efficiency. How remarkable? 26 mpg in the city and 33 mpg on the highways, or a combined figure of 28 mpg. Not only is this the best estimated efficiency we’ve ever seen on a B58-powered vehicle – beating even the smaller, lighter 2024 BMW M240i by 4 city and 1 highway mpg – it also beats out rivals with smaller engines that should theoretically be more efficient.
So, who is the 2024 BMW 5 Series laying the efficiency smack-down on? Well, the 2024 Mercedes-Benz C300 4MATIC gets a four-cylinder with a 9-speed automatic transmission. But the 2024 BMW 540i xDrive bests it by 3 city mpg and ties with it on the highway. Non-electrified Genesis G80 models (using four- or six-cylinder engines) also stand no chance. The most efficient example misses the mark by 3 mpg overall. It’s a similar story over at Audi, with the four-cylinder 2024 Audi A6 offering 2 fewer combined mpg.
More Power and More Efficient: the B58 Engine Through The Years
The B58 engine has received much praise since its debut in the 2016 BMW 3 Series. But, it wasn’t always the absolute monster it is today. It debuted with 320 horsepower and 330 pound-feet of torque in the 2016 340i. And, it offered a fairly unremarkable 23 city / 29 highway / 23 combined mpg. From 2016 until around 2020, we saw the B58 engine in several different states of tune. It generally provides between 335 and 355 horsepower and 330 and 369 pound-feet of torque. You can find it in cars like the 2019 BMW 840i and most six-cylinder G30 5 Series.
The next iteration of the inline-six-powered 3 Series debuted as the 2020 BMW M340i. While still featuring a B58 engine, it upped the power to 382 horsepower and 369 pound-feet of torque. These figures might sound familiar, as they’re, of course, the same as the rating for the Toyota Supra, M240i, and all other modern BMW vehicles powered by the B58.
Alongside the powerhouse engines in the M-lite vehicles, the newest version, a 375-horsepower unit found in the new 5 Series, X5, X7, and more, also exists. It actually makes more torque, too – 398 pound-feet, compared to 369 pound-feet in vehicles like the Supra. One thing is for certain: we’re glad that BMW’s future roadmap still includes the combustion engine. Could this be the most fuel-efficient six-cylinder engine ever produced by BMW? Only time will tell.