[winkosmosis]

When I first put my Scangauge II in my Cherokee I accidentally left it on the engine size setting for my Miata, 1.8 instead of 4.0. I calibrated it, but only with about a 1/4 tank fillup. The correction factor was 106%

Not ideal, but it should have been fairly accurate after the calibration.... And it was. It showed about 21mpg at 65mph, which is what I'd expect with my 17mpg average.

The other day I filled up, reset the gallon counter, and corrected the engine size. As you would expect, the mpg readings halved.

Then I filled up, and adjusted the gallon counter, ending up with a correction factor of 75%. Now it's reading 11-14 mpg on the highway, less than my manually calculated tank averages.

Any ideas?