The D4 has a dedicated tube to withdraw the oil and does not use a dipstick hole as suggested. The tube goes to the bottom of the sump unlike a dipstick tube. It will extract pretty much all the oil on a D4.
Yes, on a car with a traditional dipstick and drain plug, if you did it by attaching the hose to the top of the dipstick you'd not be effective. That's why on cars not designed for extraction from the factory, you insert the extraction tube through the dipstick into the bottom of the sump. This will get pretty much all the oil again.
2010 TDV6 3.0L Discovery 4 HSE
2007 Audi RS4 (B7)
Bookmarks