I've used the Penrite twice now, serviced myself. Good stuff, meets Ford spec and a good quality fluid.
Try and purchase when on sale at SuperCheap Auto, by far the cheapest option when servicing these gearbox's. I paid $61.56 / 4L for the oil, and $32.75 for the filter from Ford ($37.64 normally, ask for trade price you'll be surprised)
Had some issues with surging and this fixed it. Completed a second 6DCT450 service in short time to completely flush the trans and works a treat.
Couldn't be happier atm.
You'll need over 6L to complete the service.
Ford spec.
Reference for the part number for the external trans filter.
I've got a whole heap of photos of my service which I'll put up one day.
Will be great to support what rondeo has already supplied which was a saving grace, thanks so much!