"How much does refilling the
TDI's urea cost?"
Urea is a diesel exhaust fluid that is sprayed into the exhaust stream to reduce emissions on some diesel models and must be replenished periodically.
It costs nothing for the first three years or 36,000 miles you own a Passat TDI because the diesel exhaust fluid is included in Volkswagen's free maintenance program. Volkswagen says the urea tank should be refilled every 10,000 miles, making the first three on the house. How often a diesel vehicle needs urea can vary, so 10,000 miles is only a guide.
After the free maintenance ends, it depends on where you go for service, what they charge and how much you need. You don't have to go to a Volkswagen dealer because any repair shop should have urea on hand or be able to get it. We've seen reports from owners that they've spent as little as $10 to have the urea tank topped off (apparently with a gallon or so of the fluid) to more than $50.
The tank on the Passat holds five gallons, and a warning light that urea needs to be added should come on long before the tank runs dry. If you let it go until the tank is empty, the car won't start in order to comply with emissions regulations.
You also can purchase urea at a parts store and do it yourself. Prices ranged from $4.39 to $7.50 for a gallon and $11 to $15 for 2.5 gallons at two online parts websites we checked. Dealerships and repair shops will likely charge more. If you decide to do it yourself, handle with care. The urea fluid can damage paint finishes.