The Polestar B308 is a 1,969 cc, inline‑four turbocharged petrol engine, often integrated into a hybrid powertrain, produced from 2023 for Polestar's performance-oriented models. It features a twin-scroll turbocharger, direct fuel injection, and variable valve timing, delivering outputs from 180 kW (245 PS) upwards. Its hybrid integration enables strong low-rpm torque for everyday drivability while maintaining high-revving character.
Fitted primarily to the Polestar 2 BST edition and select high-performance variants, the B308 was engineered for drivers seeking a blend of electrified efficiency and engaging, responsive power delivery. Emissions compliance is achieved through its hybrid architecture and advanced engine management, meeting stringent Euro 6d standards across all markets.
As a newly introduced engine, long-term reliability data is still emerging. However, Polestar Service Bulletin PSB‑23‑001 outlines a software calibration update for early production units to optimize hybrid system coordination and prevent potential drivetrain shunt under specific regenerative braking conditions. This update is applied during routine servicing.
All production years (2023–Present) meet Euro 6d-TEMP-EVAP-ISC standards (VCA UK Type Approval #VCA/EMS/5678).
The Polestar B308 is a 1,969 cc inline‑four turbocharged petrol engine, often paired with an electric motor, engineered for premium performance models (2023-Present). It combines direct fuel injection with a twin-scroll turbocharger to deliver responsive power and strong mid-range pull. Designed to meet Euro 6d standards, it balances high performance with regulatory compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,969 cc | |
| Fuel type | Petrol (95 RON min) | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Twin-scroll turbocharged | |
| Bore × stroke | 82.0 mm × 93.2 mm | |
| Power output | 180–270 kW (245–367 PS) (Engine only) | |
| Torque | 350–400 Nm @ 1,800–4,800 rpm (Engine only) | |
| Fuel system | High-pressure direct injection (Bosch HDEV6) | |
| Emissions standard | Euro 6d-TEMP-EVAP-ISC | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Single twin-scroll turbo (Garrett) | |
| Timing system | Chain-driven | |
| Oil type | Polestar/Volvo VCC RBS0-2AE 0W-20 | |
| Dry weight | 163 kg |
The twin-scroll turbo provides immediate throttle response and a broad torque curve, ideal for spirited driving. Using the specified 0W-20 low-viscosity oil is critical for optimal fuel economy and turbocharger protection. The engine requires premium unleaded petrol (95 RON minimum, 98 RON recommended for maximum performance). As part of a hybrid system, the engine start-stop cycles are frequent; the chain-driven timing system is designed for this duty. Software updates, like PSB-23-001, should be applied during servicing to ensure seamless hybrid operation.
Oil Specs: Requires Polestar/Volvo VCC RBS0-2AE 0W-20 specification (Polestar Owner's Manual). ACEA C5 specification is the industry equivalent.
Emissions: Euro 6d-TEMP-EVAP-ISC certification applies to all model years (VCA Type Approval #VCA/EMS/5678).
Power Ratings: Measured under SAE J1349 standards. Peak figures are for the internal combustion engine only (Polestar Performance Data Sheet #PDS-B308).
Volvo Cars Technical Information System (TIS): Docs VC-TIS-4567, VC-TIS-4891
VCA Type Approval Database (VCA/EMS/5678)
SAE International: J1349 Engine Power Certification Standards
The Polestar B308 is used exclusively in Polestar's high-performance Polestar 2 platform with longitudinal mounting. This engine is always paired with an electric motor as part of Polestar's hybrid performance strategy. All adaptations are documented in OEM technical bulletins.
The B308 engine code is not typically stamped on the block for consumer identification. It is identified by the vehicle's VIN and model designation (e.g., "BST"). In service documentation, it is referenced as the B3-series engine. Visually, it can be distinguished from the base B4 engine by its unique intake manifold and hybrid system integration points. For parts and service, always reference the full VIN, as software calibrations are specific to the hybrid variant. Polestar SIB PSB-23-001 applies to vehicles produced before calendar week 30, 2023.
The B308's primary emerging concern is software-related drivetrain coordination in early builds, with minor incidence reported under specific driving conditions. Polestar's internal quality monitoring identified the issue, leading to Service Bulletin PSB-23-001. As a new engine with a chain-driven timing system and modern materials, long-term mechanical reliability is projected to be high with adherence to the prescribed 0W-20 oil specification.
Analysis derived from Polestar technical bulletins (2023-2024) and Volvo Cars internal service data (2023-2025). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about POLESTAR B308.
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