This indicates a mechanical failure. We've done many long drives... and cruising at 80 miles per hour we still get 35-36 mpg... and we've done this same drive in the same tire/weather conditions and still gotten 36 mpg.

I have a hunch that there is some type of "hybrid" feature failure that when the doohicky dies... it leaves you with an ordinary Altima that runs perfectly fine.

Gripper IGH LLoyd... you guys really know car mechnics inside out. Is there any feature of the car that could drop out of function and leave someone with a normal (non hybrid) car or anything like that? There is a real diversity of MPG that different people are getting... while their cars seem to run just fine and under similar conditions. I just had my MPG drop through the floor... and nothing is different about my driving or my driving conditions.