My Jetta is due its next fluid change soon and I have a few questions. First is it always required to drop the pan and change the filter every time you change the fluid? I read somewhere on here but can't seem to find it that you can use an infared therometer to guage the temp if you don't have a VAGCOM. Is this truly accurate enough? And lastly if just a fluid change without dropping the pan is ok every other change why can't you just put in exactly the same amount of fluid you drained out?