Mazda SHY8 — engine review
Mazda 2.2 SKYACTIV-D SHY8 Engine (184 hp): Experiences, Problems, Fuel Consumption and Used Car Buying Tips
Key points (TL;DR)
- Great performance: With 184 hp and 445 Nm of torque, the engine easily handles heavier bodies such as the CX-5 and Mazda 6.
- Engine timing: Uses a timing chain, not a timing belt. It is reliable but requires high-quality lubrication.
- Typical diesel issue: Fuel dilution of engine oil due to frequent DPF regenerations in city driving.
- Soot build-up: Due to low compression and a specific EGR system, the intake manifold is prone to soot (carbon) deposits.
- BiTurbo system: Provides linear acceleration without “turbo lag”, but the cost of eventual replacement is very high.
- Not for city driving: This engine shines on the highway; short trips quickly kill the DPF and EGR systems.
Contents
- Introduction
- Technical Specifications
- Reliability and Maintenance
- Specific Components and Costs
- Fuel Consumption and Performance
- Additional Options and Modifications
- Transmission and Drivetrain
- Buying Used and Conclusion
Introduction
Mazda’s 2.2 SKYACTIV-D engine has for years been the subject of debate among mechanics and drivers. The version with the code SHY8, delivering 184 hp, represents a more mature, revised generation of this engine, installed in the facelifted Mazda 6 (GJ) and Mazda CX-5 (KF) models from 2018 and 2021 respectively. In this iteration, engineers solved many of the early-series teething problems (such as camshaft issues), but kept the specific low-compression philosophy for diesel engines. The result is an extremely refined engine, with power delivery reminiscent of petrol units, yet it still carries certain demands in terms of use and maintenance that owners must be prepared for.
Technical Specifications
| Parameter | Value |
|---|---|
| Engine displacement | 2191 cc |
| Power | 135 kW (184 hp) |
| Torque | 445 Nm |
| Engine code | SHY8 |
| Injection type | Common Rail (Direct injection) |
| Induction | BiTurbo (Two turbochargers), Intercooler |
Reliability and Maintenance
Timing system and major service
The Mazda 2.2 SKYACTIV-D uses a timing chain. This means there is no classic “major service” in the sense of replacing a timing belt every 100,000 km. However, the chain is not eternal. Its lifespan directly depends on the quality of the oil and change intervals. Chain inspection is recommended after 200,000 km, and the first symptom of stretch is a metallic rattle on cold start. Replacing the full chain set is considered expensive (depends on the market). Standard service inspections that include replacement of the auxiliary belt, idlers, tensioner and water pump are usually done between 120,000 km and 150,000 km, depending on condition.
Oil: Quantity, grade and rising level
This engine takes about 5.1 to 5.5 liters of oil (including the filter). Only fully synthetic oil of grade 0W-30 or 5W-30 that meets the ACEA C3 (Low SAPS) standard is recommended, which is crucial because of the DPF filter. What is specific to Mazda diesels is that they rarely “consume” oil in the classic sense. A more common problem is a rising oil level on the dipstick. Due to DPF regenerations, excess unburnt fuel runs down the cylinder walls into the sump and dilutes the oil. On the dipstick there is an “X” mark above the maximum. If the oil level reaches the “X” mark, the oil is dangerously diluted and must be changed immediately, regardless of mileage. It is recommended to change the oil every 10,000 to 12,000 km, ignoring factory long-life intervals.
Injectors and fuel injection system
The injection system relies on advanced piezoelectric injectors (usually Denso). Due to the low compression ratio (14:1), injection must be extremely precise. The injectors are long-lasting and easily cover 200,000 to 250,000 km with good-quality fuel. However, they are very sensitive to impurities and water in the system. When they fail, refurbishment is often impossible or not cost-effective, and new injectors are very expensive (depends on the market). Symptoms of injector issues include rough idle, increased black smoke (if the DPF fails to trap it) and a sharper, “hammering” engine sound while driving.
Specific Components and Costs
BiTurbo system
This engine features a BiTurbo setup – one smaller turbocharger is responsible for quick response at low revs, while the larger one takes over at higher revs. This solves the “turbo lag” problem and gives that characteristic, almost petrol-like acceleration feel. The service life of the turbos is solid, often over 250,000 km, but they are absolutely dependent on oil pressure and quality. If the pickup screen in the oil pan gets clogged due to carbon build-up, the turbos are the first to fail because of lack of lubrication. Replacing or overhauling the entire assembly falls into the category of very expensive repairs (depends on the market).
EGR, DPF and intake manifold cleaning
The low compression ratio requires intensive EGR valve operation in order to reduce NOx emissions before the gases reach the exhaust. The consequence is extreme soot build-up in the intake manifold and on the intake valves. Symptoms include loss of performance, slight jerking and frequent DPF regenerations. Intake cleaning (most commonly using the “walnut blasting” method with crushed walnut shells) is recommended every 100,000 to 150,000 km. The DPF filter is, as usual, prone to clogging if the car is driven predominantly in stop-and-go city conditions.
AdBlue system (SCR)
To meet strict Euro 6d standards, the SHY8 version is equipped with an SCR catalyst and uses AdBlue fluid. The system effectively cleans exhaust gases but introduces additional potential failures. The most common issues include AdBlue pump failure, heater failure in the tank (especially during harsh winters when the fluid crystallizes) and problems with NOx sensors. Maintenance implies using only fresh, good-quality urea. Failures in this system do occur and are expensive to fix (depends on the market).
Fuel Consumption and Performance
Real-world fuel consumption
With a 2.2-liter displacement and substantial power, fuel economy depends on the chassis it is installed in. In the Mazda 6 (sedan or wagon) with front-wheel drive, city consumption is around 7.5 to 8 l/100 km. If the engine is paired with AWD and a heavier body such as the Mazda CX-5, real-world city driving will require between 8.5 and 9.5 l/100 km.
Driving dynamics and highway
This engine is anything but “lazy”. With 445 Nm of torque available at very low revs, it handles the weight of the CX-5 effortlessly, while turning the Mazda 6 into a serious cruiser. The engine truly shines on the highway. At 130 km/h in sixth gear, it cruises at a very relaxed 2,000 to 2,200 rpm (depending on gear ratios). Under these conditions the cabin is extremely quiet, and fuel consumption drops to an excellent 6 to 7 l/100 km.
Additional Options and Modifications
Chiptuning (Stage 1 remap)
The BiTurbo architecture leaves room for modifications. A safe Stage 1 remap can raise power from 184 hp to around 210–220 hp, while torque approaches about 500 Nm. However, moderation is advised. Excessive torque increase can shorten the life of the hydraulic automatic transmission, while increased fuel injection raises exhaust temperatures, putting additional stress on the DPF and turbos. Pushing this particular engine “to the limit” is not recommended.
Transmission and Drivetrain
Types of transmissions
Depending on trim and model, the SHY8 is paired with a 6-speed manual or a 6-speed automatic SKYACTIV-Drive transmission. Mazda’s automatic is not a dual-clutch gearbox (like DSG), but a reliable hydraulic automatic with a torque converter that features a lock-up clutch, giving it shift speeds similar to newer-generation automatics while retaining the smoothness of a classic converter.
Transmission failures and maintenance
Manual gearboxes are precise and robust, but they always come with a dual-mass flywheel. Due to the high torque (445 Nm), the flywheel usually fails between 150,000 and 200,000 km, especially if the driver likes to accelerate hard from very low revs. A clutch kit with dual-mass flywheel is expensive (depends on the market).
Automatic transmissions are extremely reliable under one condition: regular oil changes. Although some claim the oil is “lifetime”, experts recommend changing the automatic transmission fluid every 60,000 km (preferably using a machine flush). If this is neglected, the valves inside the valve body begin to stick due to metal particles, which manifests as jerks when shifting from second to third gear. If the vehicle has an AWD (4x4) system, oil changes in the transfer case and rear differential are also mandatory, likewise at around 60,000 km.
Buying Used and Conclusion
What to check before buying?
When inspecting a used car with the 2.2 SHY8 engine, be sure to pay attention to the following:
- Engine oil level: Pull out the dipstick. If the level is close to or above the “X” mark, the owner has been driving in the city for too long without proper regenerations, and the engine is prone to crankshaft bearing damage.
- Cold start: Listen to the chain during the first 5 seconds of operation. Rattling indicates the need to replace the timing set.
- Diagnostics (OBD): Crucial. Check injector corrections, the amount of ash in the DPF and the time elapsed since the last successful regeneration.
- Turbo sound: Whining under load may indicate a problem with one of the turbochargers.
Who is this engine for?
The Mazda 2.2 SKYACTIV-D (184 hp) is an engine for serious travellers. If you need a car for long trips, intercity routes and highway driving, this engine will reward you with exceptional comfort, power and reasonable fuel consumption. On the other hand, if your daily routine consists of taking the kids to school and 5 km of stop-and-go driving to work and back, stay away from this engine. City use literally chokes it (DPF, EGR, oil dilution) and will lead to extremely expensive repairs that wipe out any savings on fuel. For city driving, Mazda’s petrol engines are a far better choice.
