The feature appeared mainly on certain vehicles from the late 1970s through the 1980s, when fuel efficiency became increasingly important. The downside was slower acceleration because the transmission prioritized economy instead of performance.
Modern Eco modes use computers to adjust several systems, including throttle response and transmission behavior, while the older “E” setting mainly changed shift timing. It worked somewhat like an early version of today’s fuel-saving driving modes.
Drivers who find an “E” setting on an older vehicle may find it useful for steady, flat-road cruising, but “D” is generally better when stronger acceleration, hills, towing, or frequent stop-and-go driving are involved.
