I can't believe jcl changes his engine oil at 20,000km and claims no sludge build up. Ridiculous. To be honest. I'm a new to owning a BMW(2003 x5 4.4i). I've owned it for about 4months now. I like to tinker and fix cars and drive older model cars instead of newer cars. Older cars just have more soul and character to drive. Anyways..before owning my first BMW I knew what I was getting into. BMW already have a bad name for not being reliable..and it goes to show why.... Service intervals. Its a joke when I see 20,000kms+ engine oil service. Its no wonder why BMW leak so much. In this 4month of owning my x5 there has been afew suprises during fixes. I'm so surprised that certain gaskets can even get so brittle or can even happen! Or gaskets literally disappearing/deteriorated. Coming from a Honda car enthusiast, racing them and modifying them.. I'll guarantee you now..my 2000 integra type R(210,000km)/ and 1994 civic with a 2002 model engine dropped in, is internally cleaner and healthier than most of these BMW here period. I have changed heaps of gaskets and worked on alot of cars(non European)..but these BMW are on another level of "how can this even happen".

Oil changes is important. These bmw's wouldnt leak or have so much dam trouble if oil service was done on a regular basis and not by following the dam service light.

Put it this way, engine oil is there not just to lubricate but to also keep engine temperature down(which everyone knows). But keeping good oil in the motor does wonders especially on gaskets and seals keeping them 'rubbery' and well conditioned as they should. Keeping temperature down meaning less expansions on seals and motor.
JCL you may think your motor is healthy.. But internally you don't know what's happening..especially when engine oil is suppose to keep our famous x5 timing chain guides lubed and keeping em from getting so brittle. If anyone's interested I'll even post one of my Honda type R motors that currently sitting on 210,000kms opened.. Which looks almost brand new and HARDLY leaks and see more track racing time too. Despite the BMW having afew troubles.. I still love the thing. Next on the list is valley pan gaskets and manifold gaskets while I'm at it.

BTW whoever says spending 80-110$ every 3month - 5months is a waste of money... Well I rather spend that 110 every 3months then spend 1000$ money fixing.