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The 4 Series Convertible offers all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The MX-5 Miata 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 MX-5 Miata only offers a rear monitor.
Compared to metal, the 4 Series Convertible’s plastic fuel tank can withstand harder, more intrusive impacts without leaking; this decreases the possibility of fire. The Mazda MX-5 Miata has a metal gas tank.
Both the 4 Series Convertible and the MX-5 Miata 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 rearview cameras.
The BMW 4 Series Convertible weighs 1544 to 1989 pounds more than the Mazda MX-5 Miata. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts. Crosswinds also affect lighter cars more.
The 4 Series Convertible comes with a full 4-year/50,000-mile basic warranty, which covers the entire car and includes 24-hour roadside assistance. The MX-5 Miata’s 3-year/36,000-mile basic warranty expires 1 year and 14,000 miles sooner.
The 4 Series Convertible’s corrosion warranty is 7 years longer than the MX-5 Miata’s (12 vs. 5 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. Mazda doesn’t pay scheduled maintenance for the MX-5 Miata.
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 MX-5 Miata’s 100-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 MX-5 Miata’s battery is in the hot engine compartment.
J.D. Power and Associates rated the 4 Series Convertible first among compact premium cars in their 2018 Initial Quality Study. The MX-5 Miata 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 Mazda vehicles. J.D. Power ranks BMW 11th in initial quality, above the industry average. With 13 more problems per 100 vehicles, Mazda is ranked 22nd, below the industry average.
J.D. Power and Associates’ 2019 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that BMW vehicles are more reliable than Mazda vehicles. J.D. Power ranks BMW 7th in reliability, above the industry average. With 37 more problems per 100 vehicles, Mazda is ranked 21st.
The 430i Convertible’s standard 2.0 turbo 4 cyl. produces 67 more horsepower (248 vs. 181) and 107 lbs.-ft. more torque (258 vs. 151) than the MX-5 Miata’s 2.0 DOHC 4 cyl. The 440i Convertible’s standard 3.0 turbo 6 cyl. produces 139 more horsepower (320 vs. 181) and 179 lbs.-ft. more torque (330 vs. 151) than the MX-5 Miata’s 2.0 DOHC 4 cyl.
Regenerative brakes improve the 4 Series Convertible’s fuel efficiency by converting inertia back into energy instead of wasting it. The MX-5 Miata 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 MX-5 Miata doesn’t offer an automatic engine start/stop system.
The 4 Series Convertible has 3.9 gallons more fuel capacity than the MX-5 Miata (15.8 vs. 11.9 gallons), for longer range between fill-ups.
The BMW 4 Series Convertible comes standard with an automatic transmission, for driver comfort, especially in the city. Automatic costs extra on the MX-5 Miata.
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 MX-5 Miata.
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 Mazda MX-5 Miata is not available with all wheel drive.
For better stopping power the 4 Series Convertible’s brake rotors are larger than those on the MX-5 Miata:
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 MX-5 Miata are solid, not vented.
For better traction, the 4 Series Convertible has larger standard tires than the MX-5 Miata (225/45R18 vs. 195/50R16). The 4 Series Convertible’s optional tires are larger than the largest tires available on the MX-5 Miata (F:225/40R19 & R:255/35R19 vs. 205/45R17).
The 4 Series Convertible’s standard tires provide better handling because they have a lower 45 series profile (height to width ratio) that provides a stiffer sidewall than the MX-5 Miata Sport’s standard 50 series tires. The 4 Series Convertible’s optional 225/40R19 front and 255/35R19 rear tires have a lower 40 series front and 35 series rear profile than the MX-5 Miata Club/Grand Touring’s 45 series tires.
For better ride, handling and brake cooling the 4 Series Convertible has standard 18-inch wheels. Smaller 16-inch wheels are standard on the MX-5 Miata Sport. The 4 Series Convertible’s optional 19-inch wheels are larger than the 17-inch wheels on the MX-5 Miata Club/Grand Touring.
The BMW 4 Series Convertible’s wheels have 5 lugs for longer wheel bearing life, less chance of rotor warping and greater strength. The Mazda MX-5 Miata only has 4 wheel lugs per wheel.
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 MX-5 Miata doesn’t offer run-flat tires.
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 MX-5 Miata’s suspension doesn’t offer adjustable shock absorbers.
The 4 Series Convertible has vehicle speed sensitive variable-assist power steering, for low-effort parking, better control at highway speeds and during hard cornering, and a better feel of the road. The MX-5 Miata doesn’t offer variable-assist power steering.
For a smoother ride and more stable handling, the 4 Series Convertible’s wheelbase is 19.7 inches longer than on the MX-5 Miata (110.6 inches vs. 90.9 inches).
For better handling and stability, the track (width between the wheels) on the 4 Series Convertible is 1.9 inches wider in the front and 3.5 inches wider in the rear than on the MX-5 Miata.
The 4 Series Convertible has standard seating for 4 passengers; the MX-5 Miata can only carry 2.
The 4 Series Convertible has a much larger trunk with its top down than the MX-5 Miata (7.8 vs. 4.6 cubic feet). The 4 Series Convertible has a much larger trunk with its top up than the MX-5 Miata (13.1 vs. 4.6 cubic feet).
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 MX-5 Miata’s liftover is 32 inches.
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 MX-5 Miata doesn’t offer a hands-free gesture to open its trunk, forcing you to put cargo down if your hands are full.
The 4 Series Convertible uses gas struts to support the hood for easier service access. The MX-5 Miata 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 4 Series Convertible has a maintenance free battery for long life without checking the battery’s water level. The MX-5 Miata doesn’t have a maintenance free battery, so the water level in the battery’s cells must be checked often to prevent damage.
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 MX-5 Miata 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 MX-5 Miata doesn’t offer a heads-up display.
The 4 Series Convertible’s front and rear power windows all open or close fully with one touch of the switches, making it more convenient at drive-up windows and toll booths, or when talking with someone outside the car. The MX-5 Miata’s power window switches have to be held the entire time to close them fully. Only its front windows open automatically.
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 MX-5 Miata can only operate the windows from inside the vehicle, with the ignition on.
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 MX-5 Miata Sport/Club’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 MX-5 Miata doesn’t offer heated windshield washer nozzles.
The 4 Series Convertible’s sun-visors swivel front-to-side to block glare from the side windows. The MX-5 Miata’s visors are fixed into the windshield header.
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 MX-5 Miata’s mirror doesn’t automatically adjust for backing.
The 4 Series Convertible’s standard dual zone air conditioning allows the driver and front passenger to choose two completely different temperatures so people with different temperature preferences won’t have to compromise. This makes both the driver and front passenger as comfortable as possible. The MX-5 Miata doesn’t offer dual zone air conditioning.
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 MX-5 Miata 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 MX-5 Miata doesn’t offer an adaptive cruise control.
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 MX-5 Miata doesn’t offer an automated parking system.
The BMW 4 Series comes in coupe, convertible and four-door hatchback bodystyles; the Mazda MX-5 Miata isn’t available as a coupe or four-door.
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 MX-5 Miata is rated higher at a number “10” rate.
According to The Car Book by Jack Gillis, the 4 Series Convertible is less expensive to operate than the MX-5 Miata because typical repairs cost much less on the 4 Series Convertible than the MX-5 Miata, including $203 less for a fuel pump and $568 less for a power steering pump.
The BMW 4 Series outsold the Mazda MX-5 Miata by over three to one during 2018.
© 1991-2018 Advanta-STAR Automotive Research. All rights reserved.
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