We've been involved for the last ten months with fighting cancer. Since January, my truck probably has had less than 1,000 miles put on it; it's too tall for Maureen to get into for all the medical appointments and our other local travel.

It had an almost full DEF tank when this all started. So that stuff has been sitting through typical ambient summer temperatures in northern Illinois while being driven only occasionally.

I know there is a shelf life to think about when purchasing DEF. What about its life when it is in the vehicle?