2020 BMW 4 Series Convertible vs. 2019 Porsche 911

Detailed Review, Specifications & Comparison

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Safety

The 4 Series Convertible’s lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane. The 911 doesn’t offer a lane departure warning system.

The 4 Series Convertible offers an optional Side and Top View Cameras to allow the driver to see objects all around the vehicle on a screen. The 911 only offers a rear monitor and front and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the sides.

To help make backing safer, the 4 Series Convertible’s cross-path warning system uses wide-angle radar in the rear bumper to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. The 911 doesn’t offer a cross-path warning system.

Both the 4 Series Convertible and the 911 have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras and available all wheel drive.

Warranty

BMW pays for scheduled maintenance on the 4 Series Convertible for 2 years and 26000 miles longer than Porsche pays for maintenance for the 911 (3/36,000 vs. 1/10,000).

There are over 82 percent more BMW dealers than there are Porsche dealers, which makes it much easier should you ever need service under the 4 Series Convertible’s warranty.

Reliability

J.D. Power and Associates rated the 4 Series Convertible first among compact premium cars in their 2018 Initial Quality Study. The 911 isn’t in the top three in its category.

From surveys of all its subscribers, Consumer Reports’ December 2018 Auto Issue reports that BMW vehicles are more reliable than Porsche vehicles. Consumer Reports ranks BMW 3 places higher in reliability than Porsche.

Fuel Economy and Range

On the EPA test cycle the 4 Series Convertible gets better fuel mileage than the 911 Cabriolet:

MPG

4 Series Convertible

RWD

Auto

430i 2.0 turbo 4 cyl.

23 city/34 hwy

440i 3.0 turbo 6 cyl.

22 city/29 hwy

AWD

Auto

430i 2.0 turbo 4 cyl.

22 city/32 hwy

440i 3.0 turbo 6 cyl.

20 city/28 hwy

911 Cabriolet

RWD

Manual

3.0 turbo 6 cyl.

20 city/29 hwy

S 3.0 turbo 6 cyl.

20 city/28 hwy

GTS 3.0 turbo 6 cyl.

18 city/26 hwy

Auto

3.0 turbo 6 cyl.

22 city/28 hwy

S 3.0 turbo 6 cyl.

22 city/28 hwy

GTS 3.0 turbo 6 cyl.

20 city/26 hwy

AWD

Manual

3.0 turbo 6 cyl.

19 city/28 hwy

S 3.0 turbo 6 cyl.

19 city/28 hwy

GTS 3.0 turbo 6 cyl.

18 city/26 hwy

Auto

3.0 turbo 6 cyl.

21 city/28 hwy

S 3.0 turbo 6 cyl.

21 city/28 hwy

GTS 3.0 turbo 6 cyl.

20 city/26 hwy

Environmental Friendliness

In its Green Vehicle Guide, the U.S. Environmental Protection Agency (EPA) rates the BMW 4 Series Convertible higher (3 to 7 out of 10) than the Porsche 911 (1). This means the 4 Series Convertible produces up to 47 pounds less smog-producing pollutants than the 911 every 15,000 miles.

Transmission

The BMW 4 Series Convertible comes standard with an automatic transmission, for driver comfort, especially in the city. Automatic costs extra on the 911.

An eight-speed automatic is standard on the BMW 4 Series Convertible, for better acceleration and lower engine speed on the highway. Only a seven-speed automatic is available for the 911.

Tires and Wheels

Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires standard on the 4 Series Convertible can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The 911 doesn’t offer run-flat tires.

Suspension and Handling

For a smoother ride and more stable handling, the 4 Series Convertible’s wheelbase is 14.1 inches longer than on the 911 (110.6 inches vs. 96.5 inches).

For better handling and stability, the track (width between the wheels) on the 4 Series Convertible is 1.5 inches wider in the rear than the average track on the 911.

The 4 Series Convertible’s front to rear weight distribution is more even (49% to 51%) than the 911’s (40.1% to 59.9%). This gives the 4 Series Convertible more stable handling and braking.

Chassis

The 4 Series Convertible’s standard power retractable hardtop allows a seamless transition from an open car, to a completely sealed coupe. The 911 doesn’t offer a retractable hardtop.

Passenger Space

Because it has more passenger and cargo room, the EPA rates the 4 Series Convertible a Subcompact car, while the 911 Cabriolet is rated a Minicompact.

The 4 Series Convertible has 22 cubic feet more passenger volume than the 911 Cabriolet (90 vs. 68).

Cargo Capacity

The 4 Series Convertible has a much larger trunk with its top down than the 911 Cabriolet (7.8 vs. 5.1 cubic feet). The 4 Series Convertible has a much larger trunk with its top up than the 911 Cabriolet (13.1 vs. 5.1 cubic feet).

To make loading groceries and cargo easier when your hands are full, the 4 Series Convertible’s available trunk can be opened just by kicking your foot under the back bumper, leaving your hands completely free. The 911 doesn’t offer a hands-free gesture to open its trunk, forcing you to put cargo down if your hands are full.

Ergonomics

The 4 Series Convertible offers an optional heads-up display that projects speed and other key instrumentation readouts in front of the driver’s line of sight, allowing drivers to view information without diverting their eyes from the road. The 911 doesn’t offer a heads-up display.

If the windows are left open on the 4 Series Convertible the driver can close them all at the outside door handle. On a hot day the driver can lower the windows at the outside door handle or from a distance using the keyless remote. The driver of the 911 can only operate the windows from inside the vehicle, with the ignition on.

Comfort Access standard on the 4 Series Convertible allows you to unlock the driver’s door, trunk and start the engine all without removing a key from pocket or purse. This eliminates searching for keys before loading groceries, getting in the vehicle in bad weather or making a hurried start to your trip. The Porsche 911’s available Porsche Entry and Drive doesn’t unlock the trunk.

Heated windshield washer nozzles are standard on the 4 Series Convertible to prevent washer fluid and nozzles from freezing and help continue to keep the windshield clear in sub-freezing temperatures. The 911 doesn’t offer heated windshield washer nozzles.

For greater rear passenger comfort, the 4 Series Convertible has standard rear a/c vents to keep rear occupants more comfortable. The 911 doesn’t offer rear vents.

The 4 Series Convertible’s optional Parking Assistant can parallel park or back into a parking spot by itself, with the driver only controlling speed with the brake pedal. The 911 doesn’t offer an automated parking system.

Model Availability

The BMW 4 Series comes in coupe, convertible and four-door hatchback bodystyles; the Porsche 911 isn’t available as a four-door.

Economic Advantages

Insurance will cost less for the 4 Series Convertible owner. The Complete Car Cost Guide estimates that insurance for the 4 Series Convertible will cost $910 less than the 911 over a five-year period.

IntelliChoice estimates that five-year ownership costs (depreciation, financing, insurance, fuel, fees, repairs and maintenance) for the BMW 4 Series Convertible will be $22622 to $91912 less than for the Porsche 911.

Recommendations

The 4 Series Convertible was chosen as one of Car and Driver’s “Top Ten” in 2014. The 911 has never been a Car and Driver “Top Ten” pick.

The BMW 4 Series outsold the Porsche 911 by over three to one during 2018.

© 1991-2018 Advanta-STAR Automotive Research. All rights reserved.

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