I have a 2017 as well and believe Morgan long stopped putting the additive in before your year so you should be fine. There is a big thread on gear oil and quieting the bevel down. I believe it was the redline was the product where people had positive results with.
By the way do yourself a couple favors and get a small lift. I purchased an EZ Car Lift and it works like a charm and visit Phil’s website and Emil’s (custom Morgan). Most importantly enjoy your awesome machine.
