Nav seems to prefer kilometers while I prefer miles

[wrvond]

Some months ago the Nav unit started displaying everything in metric - distance to destination, distance to next turn, etc. . I tried going through all the preference settings to change it back to miles and such with no success. A few days later it appeared to correct itself, so I just left it at that. Now it's gone back to the metric system and I'm not finding anything that is set to metric that I can change to U.S. standard.
Help with this will be appreciated.

BTW, Waze and Google maps are not affected by this, they continue to display distances properly.