Many carmakers have chosen to integrate an electric motor along with a high-voltage battery to create a hybrid setup that improves the efficiency of a traditional engine. An alternative path involves cylinder deactivation. This technology temporarily disables select cylinders during periods of low power demand, which boosts fuel economy and cuts carbon dioxide output.

You will most often see this feature in bigger engines like the Chevrolet 5.3-liter EcoTec V8, yet certain four-cylinder units also employ it, including the Volkswagen 1.5-liter TSI Evo 2 and the Mazda 2.5-liter Skyactiv-G. Although the concept of deactivating cylinders to conserve fuel and lower emissions appears promising in theory, real-world results prove more complicated. The addition of cylinder deactivation increases both mechanical and electronic complexity. Many designs rely on oil-pressure-driven valve lifters and special valve hardware to toggle cylinders. Owners therefore face the chance that these added parts will malfunction or break, which can lead to higher oil use, fouled plugs, misfires, and other troubles. While problems are not guaranteed and depend on the specific engine, certain deactivation setups have shown repeated issues.

How the Technology Operates

Under light loads an engine often does not require every cylinder to deliver the needed power. Cylinder deactivation, called Active Fuel Management by GM, lets the control unit disable chosen cylinders until more output is required. In most gasoline engines the system stops ignition and fuel flow while holding the intake and exhaust valves shut in the disabled cylinders. The pistons keep moving, yet the trapped gases lower the effort needed to drive them. Many setups also employ hydraulically actuated lifters or rocker arms to prevent valve motion. Oil-control solenoids route pressurized oil to these parts, and the control unit handles the switch between modes. When the driver presses the accelerator or climbs a hill, the system brings the cylinders back online.

Cylinder deactivation is not a recent invention. Cadillac introduced its V8-6-4 version for the 1981 model year, allowing the engine to run on eight, six, or four cylinders. Early versions suffered from hesitation and rough transitions because engine-control systems of that era could not manage the changes smoothly. Still, Environmental Protection Agency tests from 1981 showed fuel-economy gains between 3 and 20 percent for eight-cylinder engines. Modern electronics have improved smoothness and dependability, yet the extra hardware introduces new points of failure. Benefits appear mainly during steady cruising and may shrink in stop-and-go traffic or during frequent acceleration.

Problems Linked to Cylinder Deactivation

One frequent complaint with certain engines is higher oil consumption. Oil can reach the combustion chambers through the crankcase ventilation system or other routes. Deposits in piston-ring grooves can also hinder ring movement and allow extra oil past the rings. Burning oil may foul spark plugs, cause misfires, and produce blue smoke from the exhaust. These signs can stem from other causes as well, so accurate diagnosis matters.

Lifter failures represent another risk. If a hydraulic lifter does not lock or unlock as intended, the cylinder may not function correctly, leading to ticking sounds, misfires, uneven running, or power loss. A damaged lifter can also harm the camshaft, resulting in an expensive fix. The system can produce noticeable vibrations or sound changes during mode switches. Automakers have addressed some concerns with software updates. In 2019 Mazda recalled more than 245,000 examples of the 2018-2019 CX-5 and Mazda6 plus over 17,000 units of the 2019 Mazda3 because the powertrain control module could shift modes improperly. In certain conditions a rocker arm could shift and strike internal parts, possibly causing a misfire, power loss, or stall. Dealers performed a free software update to correct the issue.

Not every engine with this technology proves unreliable. Owners should follow the recommended service intervals, use the specified oil, monitor oil levels, and address odd noises or warning lights quickly. Reviewing open recalls and service bulletins is also advisable.