Thanks finally we have some people got interested, I was afraid that I asked something very stupid

The real reason I asked was I already have one 6HP28X installed on my X5, this is making me a bit nervous because I have no idea about the milage of that transmission.

Filter and fluid will be replaced as soon as possible (When I have some time)

I don't have any warning or checklight at all, but still a bit nervous, curious about the filter type. It is a metal pan transmission.

Thanks Junkycosmos & deepblonde for the informations