25 MPG combined isn’t going to win any awards, but it’s the price of admission for the 2021 BMW Z4 M40i. This isn’t a vehicle purchased for hypermiling; it’s a roadster designed for carving canyons and enjoying the open sky, powered by a potent inline-six engine. Its buyers are willing to trade ultimate fuel efficiency for exhilarating performance and a healthy dose of style.

City and highway performance

The EPA estimates the Z4 M40i at 22 MPG in the city and 30 MPG on the highway. The city figure reflects the stop-and-go driving conditions synonymous with urban environments, where the engine is constantly accelerating and decelerating, taking a toll on fuel consumption. The highway figure, while better, acknowledges the realities of high-speed cruising, where aerodynamic drag and engine load increase, impacting overall efficiency. This spread represents a realistic expectation for how the Z4 M40i will perform in various driving scenarios, but real-world numbers can fluctuate significantly based on individual driving habits and road conditions.

Annual fuel cost

The EPA estimates that the annual fuel cost for the Z4 M40i is $2,300 per year. This figure is based on driving 15,000 miles annually, using the EPA’s combined MPG figure of 25, and assuming national average fuel prices. Keep in mind that this is an estimate, and the actual cost could vary based on your driving habits, the price of premium fuel (which is recommended for optimal performance), and the amount of city versus highway driving you do.

Real-world expectations

While the EPA provides a standardized benchmark, real-world MPG for the Z4 M40i tends to vary. Drivers who prioritize performance and frequently use the engine’s power band will likely see numbers closer to the lower end of the EPA range, sometimes dipping below 20 MPG in spirited driving. Conversely, those who adopt a more relaxed driving style and spend a significant amount of time on the highway might achieve or even slightly exceed the EPA estimates. The Z4’s driving mode selector also influences fuel economy: selecting “Eco Pro” mode can help optimize fuel consumption by adjusting throttle response and shift patterns, while “Sport” and “Sport+” modes prioritize performance and will reduce MPG.

How it compares

The Z4 M40i’s fuel economy positions it within a specific segment of performance roadsters. The Porsche 718 Boxster, for example, with its 2.0L turbo engine, achieves around 24 MPG combined. Stepping up to the Boxster S delivers similar performance to the Z4, along with similar fuel economy. The Audi TT RS, another potential competitor, delivers comparable performance but sees fuel economy figures around 22 MPG combined. For buyers considering performance first, these differences are often secondary: the Z4’s inline-six smoothness and responsiveness are compelling differentiators, and owners often care more about the driving experience than a few MPG. Comparing Z4 MPG across all years can also provide further context.

Tips to maximize efficiency

Take advantage of the Eco Pro driving mode when you’re not in the mood for spirited driving. This mode optimizes throttle response and shift patterns, keeping the engine in its most efficient operating range. While it does slightly dampen performance, it can make a noticeable difference in fuel consumption, especially during city driving.

Maintain proper tire inflation, as this is an often-overlooked aspect of fuel efficiency. Underinflated tires increase rolling resistance, forcing the engine to work harder and consume more fuel. Check your tire pressure regularly and adhere to the recommended pressure listed on the sticker inside the driver’s side door jamb.

Minimize aggressive acceleration and braking. The Z4 M40i’s inline-six is responsive and eager to rev, but frequent bursts of acceleration and hard braking waste fuel. Smooth and progressive acceleration and braking techniques are more fuel-efficient and still allow you to relish the car’s performance capabilities in a responsible manner.

Reduce unnecessary weight in the vehicle. Excess cargo adds weight, which requires more energy to move. Remove any items from the trunk or passenger compartment that you don’t need, as even small amounts of weight can cumulatively impact fuel economy. Explore all Bmw fuel economy data for similar weights and performance expectations.