[BYprodriver]

To drain max amount of used oil I drive until engine reads to the 180 mark, drive back to shop at low RPM for the last 3 blocks to minimize oil volume in heads, pull into shop & park in level spot & allow engine to idle for a full minute so scavenge pumps can pump oil out of heads into sump.
Raise Box as level as possible & remove LN magnetic drain plug as soon as possible. Remove dipstick & oil cap to aid oil flow. Remove filter as soon as it's cool enough to doso.
Porsche service manual states to allow oil to drain for 20 minutes. ( how many shops do this ?) I drain until only small drops are coming out sporadicly, usually 30 minutes+. Fill new oil filter with new JG DT40 oil as much as possible without spilling during installation.
After replacing filter & drain plug, pour in 7 quarts of JG DT40 including the oil in the filter. With car on level ground use dipstick to check oil level. Add more oil slowly until level is above lower mark on dipstick.
Start engine, wait until oil warning light goes off, & check for leaks, then go on a test-drive until engine gets up to 180 mark.Return at low rpm to park car on level surface & allow engine to idle a full minute before turning engine off. After allowing Box to sit for 20 minutes minimum, check oil level with dipstick & then oil level gauge in dash. Hopefully they show very similar results, if not trust the dipstick. If needed slowly add oil trying to get to the half way point between the dipstick marks, don't worry about trying to get it perfectly full.