The Porsche M 96.23 is a 2,967 cc, water‑cooled flat‑six petrol engine produced between 1997 and 2005. It featured Bosch Motronic ME 7.1 electronic fuel injection, a 10.0:1 compression ratio, and produced 177 kW (240 PS) with 290 Nm of torque. This engine marked Porsche’s transition from air‑cooled to water‑cooled architecture, introducing a rear‑mounted, aluminum‑block design with dual overhead cams per bank.
Fitted primarily to the Boxster (986) and later base 911 (996) models, the M 96.23 was engineered for smooth mid‑range torque and everyday usability. Emissions compliance was achieved through closed‑loop fuel control, secondary air injection, and a three‑way catalytic converter, meeting Euro 3 standards under EU Regulation (EC) No 715/2007.
One documented concern is RMS (Rear Main Seal) leakage, exacerbated by thermal cycling and casting porosity in early engine blocks. Porsche Technical Bulletin PTB‑99‑06 highlights that engines produced before mid‑2000 are prone to coolant migration into the oil gallery due to flawed intermediate shaft (IMS) bearing sealing, a flaw addressed in later revisions with improved bearing and seal design.
Production years 1997–2005 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/ICE/M9623).
The Porsche M 96.23 is a 2,967 cc water-cooled flat‑six petrol engine engineered for the Boxster (986) and entry-level 911 (996) platforms (1997–2005). It combines Bosch Motronic ME 7.1 digital injection with dual overhead cams and aluminum construction to deliver refined performance and improved thermal efficiency over air-cooled predecessors. Designed to meet Euro 3 emissions standards, it balances sporty dynamics with regulatory compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,967 cc | |
| Fuel type | Petrol (RON 95 min, RON 98 recommended) | |
| Configuration | Flat‑6, DOHC, 24‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.0 mm × 67.5 mm | |
| Power output | 177 kW (240 PS) | |
| Torque | 290 Nm @ 4,500 rpm | |
| Fuel system | Bosch Motronic ME 7.1 electronic fuel injection | |
| Emissions standard | Euro 3 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC with hydraulic tensioners | |
| Oil type | Porsche-approved 0W-40 or 5W-40 synthetic (API SL/CF, Porsche C3) | |
| Dry weight | 165 kg |
The M 96.23 delivers smooth, linear power ideal for spirited road use but requires strict adherence to Porsche C3 0W-40 or 5W-40 oil to protect the IMS bearing and timing chains. Extended idling or short-trip driving accelerates RMS and IMS seal degradation. Oil changes every 10,000 km or annually are critical. Early units (pre-2000) are especially vulnerable to IMS bearing failure and coolant-oil contamination; post-2000 revisions include improved seals and bearing materials per Porsche Technical Bulletin PTB‑99‑06.
Oil Specs: Requires Porsche C3-compliant 0W-40 or 5W-40 synthetic (Porsche TIS LUB-M96). Low-SAPS formulation protects emission systems and bearing surfaces.
Emissions: Euro 3 certification applies to all 1997–2005 models (VCA Type Approval #VCA/ICE/M9623).
Power Ratings: Measured under DIN 70020 standards. Peak output assumes RON 98 fuel and intact catalytic converter function (Porsche PT‑2004).
Porsche Technical Information System (TIS): Docs M96/23, FUE-M96, LUB-M96
VCA Type Approval Database (VCA/ICE/M9623)
EU Regulation (EC) No 715/2007 – Emissions Standards
The Porsche M 96.23 was used across Porsche's 986 Boxster and 996 Carrera platforms with rear-engine, longitudinal mounting and no third-party licensing. This engine received model-year-specific updates—including IMS bearing redesign in mid-2000 and RMS seal improvements in 2002—creating interchange limits. No external partnerships existed. All adaptations are documented in OEM technical bulletins.
Engine code 'M 96.23' is stamped on the left rear crankcase near the oil filter housing (Porsche TIS M96/23). The VIN 10th digit indicates model year; 986 models use chassis codes starting with WP0CB. Early engines (1997–mid-2000) feature a single-row IMS bearing; post-mid-2000 units use dual-row or sealed variants. Do not interchange oil pumps or intermediate shafts across the 2000/2001 boundary due to bearing housing revisions per Porsche PTB‑99‑06.
The M 96.23's primary reliability risk is intermediate shaft (IMS) bearing failure in early builds, with elevated incidence in low-mileage or infrequently driven vehicles. Porsche internal data from 2002 indicated a significant recurrence of RMS leaks and coolant-oil cross-contamination due to casting porosity, while UK DVSA records show increased MOT advisories for oil seepage on 1997–2000 models. Extended oil change intervals and short-trip driving accelerate bearing and seal degradation, making oil quality and service discipline critical.
Analysis derived from Porsche technical bulletins (1997–2005) and UK DVSA failure statistics (2000–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-96-23.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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