The 2020 BMW 840 is available in multiple trims, each with its own estimated fuel economy, here are the EPA estimates for each trim:

1. I xDrive : 21 MPG City and 27 MPG Highway
2. I : 23 MPG City and 30 MPG Highway
3. I Gran Coupe : 22 MPG City and 29 MPG Highway
4. I xDrive Gran Coupe : 20 MPG City and 27 MPG Highway

It is important to remember factors such as driving style, weather conditions, and the use of features such as Eco mode can impact fuel efficiency.