3-Stage VTEC is a multi-stage implementation of VTEC and VTEC-E, (colloquially known as dual VTEC), is implemented in some 1995-present D series engines, allowing the engine to achieve both fuel efficiency and power.
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VTEC-E (economy) was designed to achieve better fuel economy, at the cost of performance. The engine operates in "12 valve mode", where one intake valve per cylinder in the 16-valve engine remains mostly closed to attain lean burn. The lean burn mode gets the air to fuel ratio above the 14.7:1 stoichiometric ratio and thus enables extra fuel saving. It is said that the valve which remains partially closed allows fuel to drip into the combustion chamber before ignition, which helps the leaner gas/air mixture to burn within the compressed cylinder, reducing hot spots from occurring atop the piston or valves. This creates a turbulent "swirling" in the air/gas mixture which improves combustion. An average of 30 km/l 30 km/l (70.6 mpg-US) can be achieved while in lean burn at a constant speed of 60 km/h (37 mph).
From ~2500–5500 RPM, all of the engine's intake valves are used. The engine now operates like a normal fixed timing 16 valve engine.
From ~6000 RPM to the rev limiter, the engine's VTEC wild cam lobe is engaged, increasing performance and fuel consumption.