1. I did answer your question about extracting through the fill "hole" in the valve cover. "The fill hole on the valve cover does not provide direct access to the pan for extraction." The oil drains down through small channels in the head and block to the pan when added through the manufacturer designated oil fill hole on the valve cover.I am just asking this question for discussion, if the engine oil can be added through the fill hole, why can't the oil be extracted through it? Same is true for the dipstick hole, why can't we add the oil through the dipstick hole? You did not answer the question in your post.
Also, since you mentioned, what are the disadvantages of performing oil change by the top-side extraction method?
I cannot tell if you are joking or sincere.I would pump the oil through the drain plug hole. That hole is bigger than the dipstick hole at least on my 98, 1.8t. This way you can directly lubricate the oil pump sump , which is a vital engine component. The German engineering always amazes me.
Sure; but again, why?If you have a fumoto valve on the drain hole, I don't see any reason why you can't add the oil through it. After draining the old oil, pump new oil in, then close the valve while stopping the pump.
My usual VW dealer suggested just that, when I had a pan gasket leak. "Well, the gasket is bad, so the rest of the transmission can't have much life left...")The OP should know these cars don't have tranny dipstick so you replace the transmission, not the transmission fluid.
This, I'm embarrassed to admit, I have personally confirmed as impractical. The VW dealer changed my oil, and overfilled about a pint. Being nothing if not anal-retentive, I wanted to drain a bit. With a tube that would fit the dipstick neck, I actually got a siphon going - but two hours later I had all of three tablespoons out.You will need a very small hose to extract it from the dipstick tube and it will take a very, very long time to extract all the oil that way. Same goes for refilling the engine (I'm thinking like an hr. or more). Not to mention the risk of breaking the dipstick tube.