Essentially, it was a vacuum gauge that read “Power” for low vacuum and “Economy” for high vacuum instead of the actual numerical vacuum readings. A light foot on the accelerator kept the needle in the green economy range and a heavy foot put it into the red power side.
Coincidentally, in most models, this gauge was installed where the optional tach would normally be placed. Yes, the musclecar era was over by the mid-’70s.
Given today’s gas prices, we almost get nostalgic about options like this one. Have you ever owned a Pontiac with a fuel economy indicator? If so, tell us about it.