2020 BMW 4 Series Convertible vs. 2019 Buick Cascada

Detailed Review, Specifications & Comparison

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The 4 Series Convertible has standard City Collision Mitigation, which use forward mounted sensors to warn the driver of a possible collision ahead. If the driver doesn’t react and the system determines a collision is imminent, it automatically applies the brakes at full-force in order to reduce the force of the crash or avoid it altogether. The Cascada has a collision warning system without the crash-mitigating brake feature that could reduce stopping distances.

The 4 Series Convertible offers all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The Cascada doesn’t offer all-wheel drive.

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 Cascada 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.

The 4 Series Convertible’s blind spot warning system uses digital cameras monitored by computer to alert the driver to moving objects in the vehicle’s blind spots where the side view mirrors don’t reveal them and moves the vehicle back into its lane. The Cascada doesn’t offer a system to reveal objects in the driver’s blind spots.

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 Cascada doesn’t offer a cross-path warning system.

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


The 4 Series Convertible’s corrosion warranty is 6 years longer than the Cascada’s (12 vs. 6 years).

BMW pays for scheduled maintenance on the 4 Series Convertible for 3 years and 36,000 miles. BMW will pay for oil changes, lubrication and any other required maintenance. Buick only pays for the first scheduled maintenance visit on the Cascada.


To reliably power the ignition and other systems and to recharge the battery, the 4 Series Convertible has a standard 170-amp alternator (210-amp - 4 Series Convertible 6 cyl.). The Cascada’s 140-amp alternator isn’t as powerful.

The battery on the 4 Series Convertible is in the trunk, which protects it from hot underhood temperatures that can degrade battery life. By keeping the 4 Series Convertible’s battery 20 to 30 degrees cooler, its life is increased by years. The Cascada’s battery is in the hot engine compartment.

A reliable vehicle saves its owner time, money and trouble. Nobody wants to be stranded or have to be without a vehicle while it’s being repaired. Consumer Reports rates the 4 Series Convertible’s reliability 23 points higher than the Cascada.

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

J.D. Power and Associates’ 2018 Initial Quality Study of new car owners surveyed provide the statistics that show that BMW vehicles are better in initial quality than Buick vehicles. J.D. Power ranks BMW 11th in initial quality, above the industry average. With 8 more problems per 100 vehicles, Buick is ranked 16th, below the industry average.

From surveys of all its subscribers, Consumer Reports’ December 2018 Auto Issue reports that BMW vehicles are more reliable than Buick vehicles. Consumer Reports ranks BMW 11 places higher in reliability than Buick.


The 430i Convertible’s standard 2.0 turbo 4-cylinder produces 48 more horsepower (248 vs. 200) and 37 lbs.-ft. more torque (258 vs. 221) than the Cascada’s 1.6 turbo 4-cylinder. The 440i Convertible’s standard 3.0 turbo 6-cylinder produces 120 more horsepower (320 vs. 200) and 109 lbs.-ft. more torque (330 vs. 221) than the Cascada’s 1.6 turbo 4 cylinder.

Fuel Economy and Range

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


4 Series Convertible


430i 2.0 turbo 4 cyl.

23 city/34 hwy

440i 3.0 turbo 6 cyl.

22 city/29 hwy


430i 2.0 turbo 4 cyl.

22 city/32 hwy



1.6 turbo 4 cyl.

21 city/29 hwy

Regenerative brakes improve the 4 Series Convertible’s fuel efficiency by converting inertia back into energy instead of wasting it. The Cascada doesn’t offer a regenerative braking system.

In heavy traffic or at stoplights the 4 Series Convertible’s engine automatically turns off when the vehicle is stopped, saving fuel and reducing pollution. The engine is automatically restarted when the driver gets ready to move again. (Start/Stop isn’t accounted in present EPA fuel mileage tests.) The Cascada doesn’t offer an automatic engine start/stop system.

The 4 Series Convertible has 1.5 gallons more fuel capacity than the Cascada (15.8 vs. 14.3 gallons), for longer range between fill-ups.

Transmission and Drivetrain

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

All wheel drive, available in the 4 Series Convertible, provides the best traction for acceleration in wet, dry, and icy conditions. In corners, all wheel drive allows both outside wheels to provide power, balancing the car. This allows for better handling. The Buick Cascada is not available with all wheel drive.

Brakes and Stopping

For better stopping power the 4 Series Convertible’s brake rotors are larger than those on the Cascada:




Front Rotors

13 inches

13.4 inches

12.6 inches

Rear Rotors

11.8 inches

13 inches

11.5 inches

The 4 Series Convertible’s standard front and rear disc brakes are vented to help dissipate heat for shorter stops with less fading. The rear discs on the Cascada are solid, not vented.

Tires and Wheels

The 4 Series Convertible’s optional 255/35R19 rear tires provide better handling because they have a lower 35 series profile (height to width ratio) that provides a stiffer sidewall than the Cascada’s 40 series tires.

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 Cascada doesn’t offer run-flat tires.

Suspension and Handling

For superior ride and handling, the BMW 4 Series Convertible has fully independent front and rear suspensions. An independent suspension allows the wheels to follow the road at the best angle for gripping the pavement, without compromising ride comfort. The Buick Cascada has a rear torsion beam axle, with a semi-independent rear suspension.

The 4 Series Convertible has standard front and rear stabilizer bars, which help keep the 4 Series Convertible flat and controlled during cornering. The Cascada’s suspension doesn’t offer a rear stabilizer bar.

The 4 Series Convertible offers an available driver-adjustable suspension system. It allows the driver to choose between an extra-supple ride, reducing fatigue on long trips, or a sport setting, which allows maximum control for tricky roads. The Cascada’s suspension doesn’t offer adjustable shock absorbers.

For a smoother ride and more stable handling, the 4 Series Convertible’s wheelbase is 4.5 inches longer than on the Cascada (110.6 inches vs. 106.1 inches).

The 4 Series Convertible’s front to rear weight distribution is more even (49% to 51%) than the Cascada’s (58.2% to 41.8%). This gives the 4 Series Convertible more stable handling and braking.

For better maneuverability, the 4 Series Convertible’s turning circle is 1.6 feet tighter than the Cascada’s (37.1 feet vs. 38.7 feet).


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

Passenger Space

The 4 Series Convertible has 8 cubic feet more passenger volume than the Cascada (90 vs. 82).

The 4 Series Convertible has 2.6 inches more front headroom, .7 inches more front shoulder room, 1 inch more rear headroom, .3 inches more rear legroom and 4 inches more rear shoulder room than the Cascada.

Cargo Capacity

A low lift-over trunk design makes loading and unloading the 4 Series Convertible easier. The 4 Series Convertible’s trunk lift-over height is 26.2 inches, while the Cascada’s liftover is 31.2 inches.

A standard locking glovebox (which can’t be accessed with the valet key) keeps your small valuables safer in the 4 Series Convertible. The Cascada doesn’t offer locking storage for small valuables.

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 Cascada doesn’t offer a hands-free gesture to open its trunk, forcing you to put cargo down if your hands are full.

Servicing Ease

The 4 Series Convertible uses gas struts to support the hood for easier service access. The Cascada uses a prop rod to support its heavy hood. It takes two hands to open the hood and set the prop rod, the prop rod gets in the way during maintenance and service, and the prop rod could be knocked out, causing the heavy hood to fall on the person maintaining or servicing the car.

The engine in the 4 Series Convertible is mounted longitudinally (North-South), instead of sideways, as in the Cascada. This makes it easier to service and maintain, because the accessory belts are in front.


When two different drivers share the 4 Series Convertible, the memory system makes it convenient for both. Each setting activates different, customized memories for the driver’s seat position, outside mirror angle, climate settings and radio stations. The Cascada doesn’t offer a memory system.

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 Cascada doesn’t offer a heads-up display.

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 Buick Cascada doesn’t offer an advanced key system.

The 4 Series Convertible’s rain-sensitive wipers adjust their speed and turn on and off automatically based on the amount of rainfall on the windshield. This allows the driver to concentrate on driving without constantly adjusting the wipers. The Cascada’s standard manually variable intermittent wipers have to be constantly adjusted.

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 Cascada doesn’t offer heated windshield washer nozzles.

While driving with high beams on, sensitive light sensors available for the 4 Series Convertible detect other vehicles which could be blinded and automatically switch to low beams. The Cascada doesn’t offer automatic dimming high beams.

When the 4 Series Convertible is put in reverse, the passenger rearview mirror tilts from its original position. This gives the driver a better view of the curb during parallel parking maneuvers. Shifting out of reverse puts the mirror into its original position. The Cascada’s mirror doesn’t automatically adjust for backing.

The 4 Series Convertible has standard automatic dimming rear and side view mirrors which automatically darken quickly when headlights shine on them, keeping following vehicles from blinding or distracting the driver. The Cascada has an automatic rear view mirror, but its side mirrors don’t dim.

Both the 4 Series Convertible and the Cascada offer rear vents. For greater rear passenger comfort, the 4 Series Convertible has standard rear air conditioning vents to keep rear occupants cool in summer or warm in winter. The Cascada doesn’t offer rear air conditioning vents, only heat vents.

A built-in pollen filter removes pollen, exhaust fumes and other pollutants from the 4 Series Convertible’s passenger compartment. This helps prevent lung and/or sinus irritation, which can trigger allergies or asthma. The Cascada doesn’t offer a filtration system.

To keep a safe, consistent following distance, the 4 Series Convertible offers an optional Active Cruise Control, which alters the speed of the vehicle without driver intervention. This allows the driver to use cruise control more safely without constantly having to disengage it when approaching slower traffic. The Cascada doesn’t offer an adaptive cruise control.

To quickly and conveniently keep personal devices charged without cables tangling and wearing out, the BMW 4 Series offers an optional wireless phone charging system (Qi) in the center console. The Cascada doesn’t offer wireless personal charging.

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 Cascada doesn’t offer an automated parking system.

Model Availability

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

Economic Advantages

Insurance will cost less for the 4 Series Convertible owner. The Car Book by Jack Gillis rates the 4 Series Convertible with a number “1” insurance rate while the Cascada is rated higher at a number “10” rate.

The 4 Series Convertible will cost the buyer less in the long run because of its superior resale value. The IntelliChoice estimates that the 4 Series Convertible will retain 45.78% to 47.7% of its original price after five years, while the Cascada only retains 35.55% to 35.99%.

According to The Car Book by Jack Gillis, the 4 Series Convertible is less expensive to operate than the Cascada because it costs $310 less to do the manufacturer’s suggested maintenance for 50,000 miles. Typical repairs cost less on the 4 Series Convertible than the Cascada, including $191 less for a muffler, $28 less for front brake pads, $75 less for a fuel pump and $150 less for a power steering pump.


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

The 4 Series Convertible was chosen as one of Automobile Magazine’s “All Stars” in 2014. The Cascada has never been an “All Star.”

The BMW 4 Series outsold the Buick Cascada by almost 8 to one during 2018.

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

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