DEF

as this stuff dries it cristalizes ,so the float in the tank sticks after awhile,and the gauge becomes inaccurate.it's the white stuff you see at the pump.
on my 2011 cascadia i have gotten 7500 miles on a 26 gal. tank.

 

Yup, that's what my manual says. But my gauge shows that tank is full (after 3000 miles!) so I do not expect such a "shut down".
I have advised my dealer about this problem, will see tomorrow how much DEF I'll be able to pump into my tank...
Thanks everybody for willingness to help.
And I'll keep posted for a while...

 

KVN over here at Central our 2012 Cascadias have been having the same problem. According to the shop about 20% of our cascadias are not using DEF. They find the problem when drivers come in to fuel and find out they have gon 10000+mi and the def tank is still full. Freightliner has been good about taking care of it, and apparently the "slow down" is based off the guage so if it is full normal running. I did not have this problem but from talking to some of the drivers they did notice a slight drop in hp AFTER the DEF "problem" was fixed.