Tim wrote:
Bill, I have a friend with a new Chevy truck with the shut down system.
Yes, at 75 cruise on, he said he's getting about 28 mpg.

I remember in the early 80's the Caddilacs had that 8-6-4 system that
when it worked it did well. But it didn't work very well for long. A lot
of them caught on fire...

Lots more computer power in cars these days.