Remember that the 13 quarts is the total capacity... when you drain and then replace the filter (more drainage) there is still going to be some hydraulic oil in there.
You can probably put 11 quarts straight in. Then start adding the next quart bit by bit, checking the dipstick as it settles down. Once you're close, leave it until the next day and check the level, adding if required.
When you're in getting your Hy-Guard and filter, check with one of your dealership's mechanics as to the type of tool required to remove the hydraulic filter cap... it can make the whole job easier. In fact, ask the mechanic what size socket you'll need for the drain plug/bolt, it'll save you time going back & forth trying different ones 'til you find the right one.
Also, pick up a couple of cheap plastic storage containers (you may refer to them as 'totes') and use them to collect the old oil as it comes out = much easier to manoeuvre.
I've found that, after running your tractor around for an hour IOT warm the hydraulic oil up, park your rig on a level area. Open the drain plug first ('tote' in place). Once it's draining, unscrew the filling cap = faster drain. [go have a drink and come back in 20 minutes] Then unscrew the filter cap (2nd 'tote in place) and more oil will drain. Remove the old filter and CHECK IT for foreign objects/metal filings. Check and clean the screen.
No problems? Then put the new filter in and replace the cap snugly. Replace the drain plug/bolt and proceed to fill up with new oil as I described above.
All done. Have another drink or two. :drink: Easy-peasy.
