Our new 2010 Mercedes Sprinter passnger van aka Airstream tower, has the Urea. However, Mercedes gives you 20 starts of running the engine when the Urea is low then out. On the 21st start, it won't. They say under normal non-torcherous driving one doesn't have to refill the Urea for 10,000 miles. Just fill it when you get your oil changed. Heavier service will reduce the distance. UPS says they are refilling at 7500 mile intervals.
Jim and Chris
2001 Featherlite Vogue XLV 2 slide with Rivets-current coach, 1999 shell
Previous 22 years,
We have owned every kind of Prevost shell but an H3-40