Audi A4 B9 vs Mazda MX-5 IV: which is more reliable?
According to the MotorFiable Score, the Mazda MX-5 IV (6.8/10) has fewer serious documented faults than the Audi A4 B9 (6.4/10), mainly because of their engines.
| Item | Audi A4 B9 | Mazda MX-5 IV |
|---|---|---|
| Segment | Saloon | Saloon |
| Years | 2015–today | 2015–today |
| MotorFiable Score | 6.4 out of 10 | 6.8 out of 10 |
| Engine score | 6.8/10 | 7.5/10 |
| Most recommended engine | Audi 3.0 TFSI V6 · Buy | Skyactiv-G · Buy |
| Score for the rest of the car | 6.0/10 | 6.2/10 |
| Suspension | 7.4 out of 101 faultCritical severity | 8.8 out of 100 faults |
| Gearbox and clutch | 6.4 out of 103 faults | 7.1 out of 101 faultCritical severity |
| Electrical system | 7.1 out of 101 faultCritical severity | 7.1 out of 101 faultCritical severity |
| Electronics and infotainment | 8.9 out of 101 faultLow severity | 8.6 out of 101 faultMedium severity |
| Bodywork and interior | 6.2 out of 100 faults | 8.2 out of 101 faultMedium severity |
| Airbags and safety | 7.9 out of 101 faultHigh severity | 8.6 out of 101 faultMedium severity |
Scores out of 10: the higher, the fewer serious documented faults. How we calculate them
Main faults of the Audi A4 B9
Outside the engine
- Critical severityFrequency: OccasionalSuspensionCorrosion of the rear multi-link axle eccentric boltsYes: Audi recalled A4 B9s built between November 2019 and April 2021 because the eccentric bolts that secure the rear axle arm can corrode and break. A second campaign in 2022, for the same build period, extended the recall to uneven tyre wear caused by the same loss of geometry.Repair: €0
- Critical severityFrequency: OccasionalElectrical systemRisk of short circuit and fire due to moisture in electrical componentsAudi recalled A4 B9 units built between May 2017 and March 2020 because moisture can seep into an electrical component and cause a short circuit, with a risk of the vehicle catching fire.Repair: €0
- High severityFrequency: OccasionalAirbags and safetySeveral one-off campaigns on seat anchorage and the front airbag (2018-2021)Between 2018 and 2021, Audi ran several one-off campaigns on the A4 B9, each on a different and limited build batch: the front seat anchorage, the airbag control unit, a screw on the passenger airbag module and the windscreen adhesive that supports it.Repair: €0
In their engines
- High severityFrequency: Common3.0 TDI V6Failing water pump and cooling system leaksOn the 3.0 TDI the water pump can fail and, from 2010, overheat to the point of damaging the engine (the A6 C6 guide cites a service action). Owners also cite coolant leaks from hoses, the regulating valve and the cooler.
- High severityFrequency: Common2.0 TSI / TFSIHigh oil consumptionIt is the most repeated complaint on first-batch EA888s (2008-2012) and still appears, to a lesser extent, in later generations. The engine needs topping up between services with no visible leak or obvious smoke at first.Repair (garage): €1,500–€4,000
- Critical severityFrequency: Occasional3.0 TDI V6Camshaft breakage on the EA897 evo (CRT and CZV)On the EA897 evo engines from 2014 to early 2017 (mainly CRT, also CZV) the camshafts can break because of a material or design defect, according to the guides. Audi lists it in bulletin TPI 2043172 and the problem was considered under control from February 2017.
Main faults of the Mazda MX-5 IV
Outside the engine
- Critical severityFrequency: OccasionalGearbox and clutchUnintended downshift of the automatic gearbox caused by a transmission control unit software faultA 2019 recall affects MX-5 ND models with the automatic gearbox built between October 2016 and November 2018: faulty software could make the gearbox downshift without the driver asking it to and lock the rear wheels. It is corrected by reprogramming the gearbox control unit.
- Critical severityFrequency: OccasionalElectrical systemDC/DC converter control unit fault with risk of short circuit and fireA 2018 Safety Gate alert covers MX-5 ND models built between August 2014 and April 2017: the DC converter control unit could fail, cause a short circuit and damage the converter, with a risk of fire. It is a precautionary recall; check the chassis number at the official service centre.
- Medium severityFrequency: OccasionalBodywork and interiorUnderbody protective panel coming away on the first vehicles built in 2015A 2019 recall affects MX-5 ND models built between 26 May and 6 July 2015: the fixing of the underbody protective panel was insufficient and it could come loose, fall onto the road and damage tyres or put traffic behind at risk.
In their engines
- Medium severityFrequency: OccasionalSkyactiv-GIntake shut-off valve software issue and engine stallingOn Mazda3 BM/BN units built up to 4 July 2018, incorrect ECU programming can deposit soot on the intake shut-off valve to the point of suddenly stalling the engine; Mazda fixed it with a software update.
- Medium severityFrequency: OccasionalSkyactiv-GMicro-cracks in the fuel pump impellerBetween October 2017 and May 2020, Mazda built Mazda3 and CX-5 units with a fuel pump whose impeller can crack, swell and end up cutting off the fuel supply with the engine running; the manufacturer recalled the affected cars.
- Medium severityFrequency: OccasionalSkyactiv-GECU programming and loss of power (CX-5 II and Mazda3 IV)On the CX-5 II built between 2017 and 2019, and the 2019 Mazda3 IV, incorrect engine ECU programming can cause loss of power or the engine to stall; Mazda fixes it with a software update acknowledged by Germany's KBA.