The reason why the VTM4 fluids require changes every 15k miles is because this feature is continuously (more like continually--not all the time) engaged in automatic fashion. Continuously and automatically? Hmm, let's explain--it is not on all the time but engages at certain situations (automatic) with the driver doing nothing. VTM4 engages automatically everytime the vehicle is at full stop (in the morning or at the stop light) and you press the gas. However, once the vehicle reaches 18 mi/hr, the VTM4 disengages (this is the time when it's no longer engaged continuously but still in automatic mode--ready to engage at anytime). Until the next stop (and you press the gas again!). If the front tires spin, it, again engages to assist you in a slippery slope/road (no pun intended, lol) and, once again, disengages upon reaching 18 mi/hr and reverting to front wheel drive, again, as it normally should! A few inches of snow is not considered severe condition, nor a big rain. But they still present some challenges at times (esp when stopped at the light or parked after snow). This is when the auto engaged VTM4 is most effective--and you don't even have to know it! Normally though, any front wheel driven system can easily manage those situations. And so, it is there when you need it (like anti lock brake system) but doesn't intrude much. Now, there are instances when you want to disengage the automatic. Why? Some situations no longer suited for auto engage. You want to override the auto and lock it so it is forced to continuously engaged (and not disengage when you still need it). Like when you're stuck in mud, snow or going uphill with a heavy haul and it's raining. But be aware that once you reached 18 mi/hr, it will disengage again (so watch the speedometer). Why? To protect itself from overheating. This system is less costly than full time system--less fuel consumption, less maintenance and repairs, less parts to break, less weight and very reliable as proven by many thousands still in the road today! This is Honda"s version of having our cake and eat it, too! Not a perfect system but it works!