Most manuals state 6k or more between changes, and to change the filter every other change. The OEM tends to be very much overkill and overly ridiculous when it comes to other things, so if they say the engine is safe at those intervals and filter changes, why should we worry about it? Quality of shifting changes more than anything else, I notice after about 4k that the shifting on my C14 becomes a tad bit notchy......but the oil is still doing its job. And those recommendations are with dino not synthetic.