I have a 6 year old BMW X5 Diesel.

We've had a maintenance contract on it and as such, have never added DEF to the vehicle.

Now that contract has expired, it's time for me to start doing this.

From my little bit of reading, DEF meets a certain ISO standard and there is only one formula of it, i.e. there aren't various grades of DEF like gasoline.

So I guess what I'm asking, there really isn't different grades for different vehicles that require DEF.

Thanks.