16.00/gallon. Sounds reasonable. I do know that truck stops have a similar urea solution concentration but I did NOT know that it could be used on the X5 diesel. Good to know. Thats one of the reasons why I will not be purchasing a Q7 TDI. The Audi Q7 is not customer friendly. Only the dealer can reset the the adblue sensor. Funny thing is that the adblue fill up location is conveniently located next to the diesel fill up. Customer friendly you might think, however...in an emergency, you are able to dispense enough adblue to get you to the dealer so that the dealer can fill up the ten gallon tank. If you were to fill up the adblue(urea) tank yourself the computer will not recognize it. This is very inconvenient yet they will argue that purchasing the Audi care service plan for 740.00(45,000 miles) will save you a lot of money. Audi care service plan covers oil changes and adblue. I asked Audi the same question "What happens when the Audi Care Service plan expires?". I also worked out a calculation that showed how deceiving their advertisement for best mpg when comparing their TDI to their own GAS and competitor GAS vehicles. Got to go on the elliptical. Be back in a few....