I have a 2011 chevy silverado 3500hd, crew cab, 8' bed. Today with 11,500 miles I had 2/3 tanks of diesel and I topped it off at a Flying J gas station. Within 50 miles I got the "Water in Gas" warni...
You'll never make it 200 miles with the alarm on. It will go into limp mode long before that. I agree with ronniedean1234 and would put the additive to it. I would also top that tank off with fresh fuel.