It's probably deposit buildup on the wire wind because the gage may not get that low very often if you are in the habit of filling up before it gets to the quarter point.

Pumping in a few gallons when it is near empty several times will excercise the wiper between empty and a quarter and it may rub of the varnish.

This worked for me - for a while at least. I've removed sending units from GM cars and cleaned the wire wind, but I'm not sure if the MBZ sending unit can be disassebled enough to get to the varnish.

Anybody know?

Duke