2020 BMW M4 vs. 2019 Maserati GranTurismo Convertible

Detailed Review, Specifications & Comparison

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The M4 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 GranTurismo Convertible doesn't offer collision warning or crash mitigation brakes.

The M4’s lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane. The GranTurismo Convertible doesn’t offer a lane departure warning system.

The M4 offers an optional Side and Top View Cameras to allow the driver to see objects all around the vehicle on a screen. The GranTurismo Convertible only offers front and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the sides.

The M4’s optional 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. The GranTurismo Convertible doesn’t offer a system to reveal objects in the driver’s blind spots.

The M4 has standard BMW Assist, which uses a global positioning satellite (GPS) receiver and a cellular system to remotely unlock your doors if you lock your keys in, help track down your vehicle if it’s stolen or send emergency personnel to the scene if any airbags deploy. The GranTurismo Convertible doesn’t offer a GPS response system, only a navigation computer with no live response for emergencies, so if you’re involved in an accident and you’re incapacitated help may not come as quickly.

Both the M4 and the GranTurismo Convertible have standard driver and passenger frontal airbags, front side-impact airbags, side-impact head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights and front and rear parking sensors.


The M4’s corrosion warranty is 8 years and unlimited miles longer than the GranTurismo Convertible’s (12/unlimited vs. 4/50,000).

BMW pays for scheduled maintenance on the M4 for 3 years and 36,000 miles. BMW will pay for oil changes, lubrication and any other required maintenance. Maserati doesn’t pay scheduled maintenance for the GranTurismo Convertible.

There are almost 3 times as many BMW dealers as there are Maserati dealers, which makes it much easier should you ever need service under the M4’s warranty.


To reliably power the ignition and other systems and to recharge the battery, the M4 has a standard 209-amp alternator. The GranTurismo Convertible’s 150-amp alternator isn’t as powerful.

To reliably start during all conditions and help handle large electrical loads, the M4 has a standard 900-amp battery. The GranTurismo Convertible’s 850-amp battery isn’t as powerful.


The M4’s standard 3.0 turbo 6 cyl. produces 22 lbs.-ft. more torque (406 vs. 384) than the GranTurismo Convertible’s 4.7 DOHC V8. The M4’s optional 3.0 turbo 6 cyl. produces 22 lbs.-ft. more torque (406 vs. 384) than the GranTurismo Convertible’s 4.7 DOHC V8.

Fuel Economy and Range

On the EPA test cycle the M4 Convertible gets better fuel mileage than the GranTurismo Convertible:


M4 Convertible


3.0 turbo 6 cyl.

17 city/25 hwy


3.0 turbo 6 cyl.

16 city/22 hwy

GranTurismo Convertible


4.7 DOHC V8

13 city/20 hwy

In heavy traffic or at stoplights the M4’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 GranTurismo Convertible doesn’t offer an automatic engine start/stop system.

Environmental Friendliness

In its Green Vehicle Guide, the U.S. Environmental Protection Agency (EPA) rates the BMW M4 higher (3 out of 10) than the Maserati GranTurismo Convertible (1). This means the M4 produces up to 22.5 pounds less smog-producing pollutants than the GranTurismo Convertible every 15,000 miles.


A seven-speed automatic (SMG) is available on the BMW M4, for better acceleration and lower engine speed on the highway. Only a six-speed automatic is available for the GranTurismo Convertible.

The M4 Automatic’s optional launch control uses engine electronics to hold engine RPM’s precisely in order to provide the most stable and rapid acceleration possible, using all of the available traction. The GranTurismo Convertible doesn’t offer launch control.

Brakes and Stopping

For better stopping power the M4’s brake rotors are larger than those on the GranTurismo Convertible:




Front Rotors

15 inches

15.7 inches

14.2 inches

Rear Rotors

14.6 inches

15 inches

13 inches

The M4 offers optional heat-treated ceramic brake rotors, which last ten to twenty times as long as conventional cast iron rotors, don’t rust, don’t fade during repeated high speed braking, and their lighter weight contribute to better braking, handling and acceleration. The GranTurismo Convertible doesn’t offer ceramic brake rotors.

Tires and Wheels

For better traction, the M4 has larger front standard tires than the GranTurismo Convertible (255/40R18 vs. 245/35R20). The M4’s optional front tires are larger than the largest tires available on the GranTurismo Convertible (F:265/30R20 & R:285/30R20 vs. F:245/35R20 & R:285/35R20).

The M4’s optional tires provide better handling because they have a lower 30 series profile (height to width ratio) that provides a stiffer sidewall than the GranTurismo Convertible’s 35 series tires.


The BMW M4 may be more efficient, handle and accelerate better because it weighs about 200 to 750 pounds less than the Maserati GranTurismo Convertible.

The M4 is 8.8 inches shorter than the GranTurismo Convertible, making the M4 easier to handle, maneuver and park in tight spaces.

The M4’s standard power retractable hardtop allows a seamless transition from an open car, to a completely sealed coupe. The GranTurismo Convertible doesn’t offer a retractable hardtop.

Passenger Space

The M4 Convertible has 4.9 cubic feet more passenger volume than the GranTurismo Convertible (89.9 vs. 85).

Cargo Capacity

The M4 Convertible has a much larger trunk with its top down than the GranTurismo Convertible (7.8 vs. 6.1 cubic feet). The M4 Convertible has a much larger trunk with its top up than the GranTurismo Convertible (11 vs. 6.1 cubic feet).

The M4’s standard rear seats fold to accommodate long and bulky cargo. The GranTurismo Convertible doesn’t offer folding rear seats.

With its coupe or convertible body style, valet key, locking rear seatbacks and remote trunk release lockout, the M4 offers cargo security. The GranTurismo Convertible’s non-lockable remote release defeats cargo security.

To make loading groceries and cargo easier when your hands are full, just kicking your foot under the back bumper can open the M4’s trunk, leaving your hands completely free. The GranTurismo Convertible doesn’t offer a hands-free gesture to open its trunk, forcing you to put cargo down if your hands are full.


The M4 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 GranTurismo Convertible doesn’t offer a heads-up display.

If the windows are left open on the M4 the driver can close them all at the outside door handle. On a hot day the driver can lower the windows from a distance using the keyless remote. The driver of the GranTurismo Convertible can’t use the remote to operate the windows.

Comfort Access standard on the M4 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 Maserati GranTurismo Convertible doesn’t offer an advanced key system.

Heated windshield washer nozzles are standard on the M4 to prevent washer fluid and nozzles from freezing and help continue to keep the windshield clear in sub-freezing temperatures. The GranTurismo Convertible doesn’t offer heated windshield washer nozzles.

While driving with high beams on, sensitive light sensors available for the M4 detect other vehicles which could be blinded and automatically switch to low beams. The GranTurismo Convertible doesn’t offer automatic dimming high beams.

On extremely cold winter days, the M4’s optional heated steering wheel provides comfort, allowing the driver to steer safely and comfortably before the car heater warms up. The GranTurismo Convertible doesn’t offer a heated steering wheel.

The M4’s standard steering wheel mounted cruise control is close at hand. The GranTurismo Convertible’s standard cruise control is on an over-crowded turn signal stalk.

The M4’s optional Parking Assistant can parallel park by itself, with the driver only controlling speed with the brake pedal. The GranTurismo Convertible doesn’t offer an automated parking system.

Model Availability

The BMW M4 comes in coupe and convertible bodystyles; the Maserati GranTurismo isn’t available as a coupe.


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

The M3/M4 was chosen as one of Automobile Magazine’s “All Stars” for 13 of the last 23 years. The GranTurismo Convertible has never been an “All Star.”

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

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