Hi Guys

I am about to service the X5 on monday but had a couple of last minute questions. I was going to use a 0-30w castrol edge turbo diesel oil or a 5-30W. Does anyone know which would be better. It is a 2001 x5 with 56k on it.
secondly i was going to change the cabin filter and obviously oil filter. Do you think i need to change the air filter too. If so how difficult a job is the air filter.
I looked under the bonnet today and noticed there was some fluid which looked like water on the bit under the oil filter, i wasnt sure where it was coming from so does anyone have any clues. I was thinking of coolant leak maybe.
and last but not least should I do a coolant change. if so how is this done.
your comments are appreciated just before i take the plunge.
Thanks