2020 BMW 840i xDrive Convertible: MPG and fuel economy
The 2020 BMW 840i xDrive Convertible is rated by the U.S. Environmental Protection Agency at 23 combined MPG, with 20 MPG in the city and 27 MPG on the highway. That sits a little below the average car in the Subcompact Cars class for the same model year.
This page collects every fuel-economy figure the EPA publishes for the 2020 BMW 840i xDrive Convertible. Below you will find the headline combined, city, and highway MPG, the estimated annual fuel cost at three different driving levels, the tailpipe CO₂ emissions, and a full breakdown of the engine and drivetrain. If you want to know whether this generation got more or less efficient over the years, the year-over-year table further down covers every model year the EPA has rated.
Key takeaways
- The most efficient car in the Subcompact Cars class for the 2020 model year is the BMW i3 at 113 MPG.
- EPA estimates this car costs around $4,250 more in fuel over five years than an average new vehicle of the same model year.
- Requires premium gasoline, which typically adds about 40 to 60 cents per gallon to the EPA's annual fuel cost estimate.
Fuel economy at a glance
These are the EPA's official ratings for the 2020 BMW 840i xDrive Convertible. The numbers come from a standardised laboratory test cycle and are the same figures that appear on the window sticker of every new car. Real-world mileage varies with driving style, weather, fuel quality, and how heavily loaded the car is.
Combined MPG is a 55/45 weighted blend of the city and highway test cycles. The EPA uses it as the single number you can compare across the entire dataset, including hybrids and EVs (which use the equivalent MPGe figure).
| Combined MPG | 23 MPG |
| City MPG | 20 MPG |
| Highway MPG | 27 MPG |
| Annual fuel cost | $3,000 |
| Tailpipe CO₂ | 388 g/mi |
| Fuel type | Premium |
How the 2020 BMW 840i xDrive Convertible compares
The 2020 BMW 840i xDrive Convertible returns 23 combined MPG. Cars in the Subcompact Cars class for the same model year average 26.5 MPG, which puts this car behind the class average by about 13%.
The most efficient car in the Subcompact Cars class for the 2020 model year is the BMW i3 at 113 MPG. The bar chart below puts the BMW 840i xDrive Convertible alongside the class best and the class average so you can see the full picture.
For broader context, the average new car of the 2020 model year (across all classes) returns 27.2 MPG. Larger vehicles pull the all-cars average down, so do not use that figure on its own to judge a small car or a hybrid. The full list of the most efficient cars of the 2020 model year is on its own page.
Annual fuel cost across driving patterns
The headline annual fuel cost the EPA publishes assumes 15,000 miles of driving per year and a fuel mix of 55% city and 45% highway. The dollar figure is calculated using the EPA's current reference price for premium gasoline, which is $4.61/gallon. EPA updates that reference periodically rather than tracking live pump prices, so treat it as a window-sticker estimate rather than today's pump number.
The table below scales the EPA's number to three common driving patterns. The combined MPG and the reference fuel price stay constant, only the annual mileage changes. To get a current-prices estimate, take your local gas price and multiply by 652.2 gallons (the car's annual consumption at the rated MPG).
| Driving pattern | Estimated annual fuel cost |
|---|---|
| Light driver, 7,500 miles per year | $1,500 |
| Average driver, 15,000 miles per year | $3,000 |
| Heavy driver, 25,000 miles per year | $5,000 |
Year-over-year MPG for the BMW 840i xDrive Convertible
The EPA has rated the BMW 840i xDrive Convertible across 7 model years, from 2020 BMW 840i xDrive Convertible through 2026 BMW 840i xDrive Convertible. The numbers below are the best combined MPG figure the EPA published for each year, which lets you see when the car was at its most efficient and how recent generations stack up.
Combined MPG has stayed in roughly the same range across the run. The peak rating came with the 2023 BMW 840i xDrive Convertible at 24 MPG.
| Year | Combined MPG | Open year page |
|---|---|---|
| 2026 | 24 MPG | 2026 BMW 840i xDrive Convertible |
| 2025 | 24 MPG | 2025 BMW 840i xDrive Convertible |
| 2024 | 24 MPG | 2024 BMW 840i xDrive Convertible |
| 2023 | 24 MPG | 2023 BMW 840i xDrive Convertible |
| 2022 | 23 MPG | 2022 BMW 840i xDrive Convertible |
| 2021 | 23 MPG | 2021 BMW 840i xDrive Convertible |
| 2020 | 23 MPG | this page |
Compare against other Subcompact Cars for 2020
If you are cross-shopping the 2020 BMW 840i xDrive Convertible, the most useful comparison is against the other cars in the Subcompact Cars class for the same model year. The list below shows the highest-MPG peers, ranked from most to least efficient. Click any of them to open its full page.
The BMW i3 leads this group at 113 MPG, 90 MPG ahead of the 2020 BMW 840i xDrive Convertible.
Specifications
The 2020 BMW 840i xDrive Convertible runs a 3-liter 6-cylinder turbocharged engine paired with a automatic (s8), sending power through all-wheel drive.
Engine, transmission, and drivetrain together drive most of the variation in fuel economy across trims. A larger engine moves the car with less effort but burns more fuel. A turbo lets a small engine punch above its weight, often without much MPG penalty. All-wheel drive adds traction and weight, and usually costs a couple of MPG compared with two-wheel drive of the same engine.
- Vehicle class
- Subcompact Cars
- Engine
- 3L 6-cylinder turbocharged
- Transmission
- Automatic (S8)
- Drivetrain
- All-Wheel Drive
- Fuel type
- Premium
- Annual petroleum use
- 12.9 barrels per year
- Start-stop system
- Yes
Common questions about the 2020 BMW 840i xDrive Convertible
Quick answers to the questions people most often search for when looking up the 2020 BMW 840i xDrive Convertible.
-
Is the 2020 BMW 840i xDrive Convertible fuel efficient?
Not particularly. The 2020 BMW 840i xDrive Convertible returns 23 combined MPG, which trails the average car in the Subcompact Cars class for the same model year by about 13%. -
What MPG does the 2020 BMW 840i xDrive Convertible get?
The EPA rates the 2020 BMW 840i xDrive Convertible at 23 combined MPG, 20 MPG in city driving, and 27 MPG on the highway. Real-world numbers depend on your driving style, the weather, and how loaded the car is. -
How much does it cost to fuel a 2020 BMW 840i xDrive Convertible per year?
The EPA estimates an annual fuel cost of $3,000 for the 2020 BMW 840i xDrive Convertible. That figure assumes 15,000 miles of driving per year, a 55% city and 45% highway split, and the EPA's published average fuel price for the rated fuel grade. -
Does the 2020 BMW 840i xDrive Convertible require premium gas?
Yes. The EPA lists the 2020 BMW 840i xDrive Convertible as requiring premium gasoline. Running it on regular can reduce performance and may affect engine warranties, so it is not a recommended way to save at the pump. -
Has the BMW 840i xDrive Convertible become more fuel efficient over time?
Combined MPG has stayed close to flat across the run. Both the earliest (2020 BMW 840i xDrive Convertible, 23 MPG) and most recent (2026 BMW 840i xDrive Convertible, 24 MPG) versions sit in the same range. -
How much CO₂ does the 2020 BMW 840i xDrive Convertible emit?
Tailpipe CO₂ emissions are 388 g/mi. Multiplied across a typical year of driving (15,000 miles) that works out to about 5,820 kilograms of CO₂. -
What is the difference between the city and highway MPG of the 2020 BMW 840i xDrive Convertible?
City driving returns 20 MPG and highway driving returns 27 MPG, a gap of 7 MPG. A spread that wide is typical of cars with conventional automatic or manual transmissions, where stop-start city traffic eats more fuel than a steady highway cruise. -
What engine is in the 2020 BMW 840i xDrive Convertible?
The 2020 BMW 840i xDrive Convertible has a 3-liter 6-cylinder turbocharged engine (EPA description: SIDI). -
What transmission and drivetrain does the 2020 BMW 840i xDrive Convertible have?
The 2020 BMW 840i xDrive Convertible comes with a automatic (s8) transmission and all-wheel drive. All-wheel-drive variants typically read 1 to 3 MPG lower than the front-wheel-drive equivalent of the same engine, since the extra hardware adds weight and parasitic loss. -
How does the 2020 BMW 840i xDrive Convertible compare to the best car in its class?
The most efficient car in the Subcompact Cars class for the 2020 model year is the BMW i3 at 113 combined MPG. The BMW 840i xDrive Convertible returns 23 MPG, a gap of 90 MPG. If you are comparing on fuel economy alone, the class leader is worth a look.
Source: U.S. EPA fuel economy dataset. Annual fuel cost figures assume 15,000 miles of driving per year and a 55% city, 45% highway split. Real-world mileage varies with driving conditions, vehicle maintenance, fuel quality, and driver behaviour.