2004 BMW 645ci Convertible MPG and Fuel Economy

On this page, you will find a complete guide to the miles per gallon and fuel efficiency data for the 2004 BMW 645ci Convertible.

The 2004 BMW 645ci Convertible has 3 model options: Manual 6-spd 8-cyl, 4.4 L, Automatic (S6) 8-cyl, 4.4 L and Automatic (S6) 8-cyl, 4.4 L.

The 2004 BMW 645ci Convertible Manual 6-spd 8-cyl, 4.4 L runs on premium gasoline and is in the Subcompact Cars car class.

The 2004 BMW 645ci Convertible Automatic (S6) 8-cyl, 4.4 L runs on premium gasoline and is in the Subcompact Cars car class.

The 2004 BMW 645ci Convertible Automatic (S6) 8-cyl, 4.4 L runs on premium gasoline and is in the Subcompact Cars car class.

🛣 How Many Miles per Gallon (MPG) Does a 2004 BMW 645ci Convertible Get?

Across all models, the combined average MPG for the 2004 BMW 645ci Convertible is 17 miles per gallon.

The table below breaks down the MPG for each model option:

Model OptionCombined MPGCity MPGHighway MPG
Manual 6-spd 8-cyl, 4.4 L161321
Automatic (S6) 8-cyl, 4.4 L191624
Automatic (S6) 8-cyl, 4.4 L161321

💵 What is the Average Yearly Fuel Cost for a 2004 BMW 645ci Convertible?

The average fuel costs for all models of the 2004 BMW 645ci Convertible is $4,367.

The average fuel costs have been estimated by government regulators based on 15,000 miles driven per year, using regular gasoline, and a split of 55% city driving and 45% highway driving.

Comparing a 2004 BMW 645ci Convertible to an average vehicle over 5 years, you will spend $10,333 more on fuel.

The table below shows the fuel costs and 5-year save/spend for each model option:

Model OptionFuel Cost5-Year Save/Spend
Manual 6-spd 8-cyl, 4.4 L$4,600spend $11,500 more
Automatic (S6) 8-cyl, 4.4 L$3,900spend $8,000 more
Automatic (S6) 8-cyl, 4.4 L$4,600spend $11,500 more

The 2004 BMW 645ci Convertible is also subject to the Gas Guzzler Tax, which is a federal tax on vehicles that has a combined MPG of less than 22.5.

The tables below show how much you can expect to pay in Gas Guzzler taxes.

Model OptionGas Guzzler Tax
Manual 6-spd 8-cyl, 4.4 L$3,700
Model OptionGas Guzzler Tax
Automatic (S6) 8-cyl, 4.4 L$3,700

🛢 How Many Barrels of Petroleum Does a 2004 BMW 645ci Convertible Consume?

Across all models, the average number barrels of petroleum that the 2004 BMW 645ci Convertible will consume in one year is 18 barrels.

The majority of the world's petroleum is sourced from countries like Saudi Arabia, Russia, Iraq, and the United States.

Model OptionBarrels
Manual 6-spd 8-cyl, 4.4 L19
Automatic (S6) 8-cyl, 4.4 L16
Automatic (S6) 8-cyl, 4.4 L19

💨 How Many Grams of CO2 Does a 2004 BMW 645ci Convertible Emit?

The 2004 BMW 645ci Convertible will emit an average of about -15,000 grams of CO2 per year.

🌳 To help you understand the impact of this, a normal tree will absorb around 21,000 grams of CO2 per year. This means that roughly 1 tree would be needed to offset emissions from the 2004 BMW 645ci Convertible.

Overview

The tables below cover all of the miles per gallon, engine specifications, and emission details we have for the 3 2004 BMW 645ci Convertible model options.

Manual 6-spd 8-cyl, 4.4 L

The table below contains all of the details we have for the 2004 BMW 645ci Convertible Manual 6-spd 8-cyl, 4.4 L:

City MPG13
Highway MPG21
Combined MPG16
Save/Spend vs Average CarSpend $11,500
Gas Guzzler Tax$3,700
Fuel Cost$4,600
Fuel Type 1Premium
Barrels of Petroleum19
Grams of CO2-15,000
Trees Needed to Offset-1
DriveRear-Wheel Drive
Cylinders8
Displacement4.4
TransmissionManual 6-spd
Vehicle ClassSubcompact Cars
Start/Stop?No
Supercharged?No
Turbocharged?No

Automatic (S6) 8-cyl, 4.4 L

The table below contains all of the details we have for the 2004 BMW 645ci Convertible Automatic (S6) 8-cyl, 4.4 L:

City MPG16
Highway MPG24
Combined MPG19
Save/Spend vs Average CarSpend $8,000
Fuel Cost$3,900
Fuel Type 1Premium
Barrels of Petroleum16
Grams of CO2-15,000
Trees Needed to Offset-1
DriveRear-Wheel Drive
Cylinders8
Displacement4.4
TransmissionAutomatic (S6)
Vehicle ClassSubcompact Cars
Start/Stop?No
Supercharged?No
Turbocharged?No

Automatic (S6) 8-cyl, 4.4 L

The table below contains all of the details we have for the 2004 BMW 645ci Convertible Automatic (S6) 8-cyl, 4.4 L:

City MPG13
Highway MPG21
Combined MPG16
Save/Spend vs Average CarSpend $11,500
Gas Guzzler Tax$3,700
Fuel Cost$4,600
Fuel Type 1Premium
Barrels of Petroleum19
Grams of CO2-15,000
Trees Needed to Offset-1
DriveRear-Wheel Drive
Cylinders8
Displacement4.4
TransmissionAutomatic (S6)
Vehicle ClassSubcompact Cars
Start/Stop?No
Supercharged?No
Turbocharged?No

Link To or Reference This Page

If you use this page in your research, please reference MPG Buddy as the source.

  • "2004 BMW 645ci Convertible MPG and Fuel Economy." MPG Buddy. Accessed on January 3, 2026. https://mpgbuddy.com/cars/bmw/645ci-convertible/2004.

  • "2004 BMW 645ci Convertible MPG and Fuel Economy." MPG Buddy, https://mpgbuddy.com/cars/bmw/645ci-convertible/2004. Accessed January 3, 2026.

  • 2004 BMW 645ci Convertible MPG and Fuel Economy. MPG Buddy. Retrieved from https://mpgbuddy.com/cars/bmw/645ci-convertible/2004.