Pat Goss answers: Do cylinder deactivation systems cause engines to wear out?

Do cylinder deactivation systems cause engines to wear out faster, or is there a use for it? Based on what we see in our shops I would have to say that for the average driver and good preventive maintenance there is no measurable increased wear. But in certain very specific driving conditions where the engine remains in deactivated mode for long periods of time we have seen valve lifter, camshaft and camshaft bearing issues. We suspect this to be due to modified oil flow for the system’s active valve lifters but even here the problems seem to be extremely rare in the fleets we service. As far as things like balance, piston wear, ring wear and the host of other myths about cylinder deactivation we see none of those problems. Balance of the engine is properly maintained because these systems deactivate out of phase cylinders. On V type engines on one bank there will be one or two inactive center cylinders (V6–1/V8–2) and two active end cylinders while on the opposite bank the sequence is reversed. So there is never any such thing as an entire bank of cylinders that is disabled. These systems use active valve lifters so that during inactive operation the valves to the inactive cylinders do not open. So no air or fuel enters the cylinders, therefore no general contamination issues. Because everything is evenly spread out across the engine there are no overheating issues. Overall we would give the systems a high rating with mostly no measurable added wear. The cylinder deactivation systems are for mileage improvement and although the improvement is small per vehicle the cumulative amount of gas saved nationally and globally through tens of millions of these vehicles is substantial.

Fuel Trin is always changing Part 2

Fuel trim is always changing Part 1