http://www.xoutpost.com/articles.php?...ticle&artid=82

thats a great guide on fluids and maintenance.

personally, i do more or less depending on how i use the vehicle. heavily used vehicles get more attention (ie: my track cars gets an oil change every 2-4 weeks, tranny/diff oil change every 4-6 months, spark plugs once a 6-12 months, etc and my street cars are much much less) my old x5 got its oil changed every 6 months, brake fluid flushed once a year, tranny/diff would have been every 2 years, plugs every 2 years, etc) - this is overkill for most people... just peace of mind for me and i don't mind the cost of that.