Mitsubishi 4B12 MIVEC Engine Specs

The Mitsubishi 4B12 MIVEC is a 2.4-liter naturally aspirated inline-four petrol engine produced since 2005, used primarily in the Mitsubishi Outlander, Lancer, and Galant as the brand's mainstream mid-size engine. Positioned as a versatile, general-purpose unit rather than a performance engine, the 4B12 was designed to offer a reasonable balance of torque, smoothness, and efficiency for family-oriented vehicles.

Producing 170hp and 226Nm of torque from 2,359cc, the 4B12 uses a DOHC 16-valve aluminum head with Mitsubishi's MIVEC variable valve timing system and a compression ratio of 10.5:1. Its larger displacement compared with Mitsubishi's smaller four-cylinder engines gives it noticeably stronger low-end and mid-range torque, well suited to the heavier Outlander SUV application in particular, while a timing chain drive keeps long-term maintenance costs down by eliminating scheduled belt replacement.

Reliability has generally been good, though a few items deserve attention on higher-mileage examples. The MIVEC actuator, responsible for variable valve timing, depends on clean oil to operate correctly, and consistent oil changes with the recommended viscosity help keep it functioning properly over the engine's life; a malfunctioning actuator can produce rough idle or reduced performance. Some owners report gradually increasing oil consumption as mileage climbs, which is worth monitoring with regular level checks rather than relying solely on scheduled top-ups. The timing chain, while generally durable, can develop stretch over very high mileage, sometimes producing a rattling noise on cold starts that's worth having assessed. The balance shaft system, used to smooth out four-cylinder vibration at this displacement, is a wear item over the very long term and benefits from being included in broader engine inspections. Carbon buildup on the intake valves can develop gradually over high mileage, a trait common to most modern engines regardless of manufacturer, and is generally addressed with periodic intake cleaning if performance or smoothness noticeably declines. With reasonable maintenance, the 4B12 has proven itself a durable and dependable choice across Mitsubishi's family and crossover lineup.