Remember that long ago the old, original STA-BIL was primarily just plain old ethanol with red coloring with some cleaning additives added to it. It was added to pure gasoline prior to storage back then (before we ended up with this ethanol blended crap) to absorb water/condensation that could form in a tank of gas if stored for a while and end up in the pure gasoline where it would not mix with the gas and could be sucked up and pumped through fuel injectors and carbs and into the cylinder and such where water causes serious problems. Since ethanol is already in today's fuels and bonds with water, water building up in stored fuel in the tank is no longer a problem. However, because we now have gas that contains 10%+ ethanol we have a far more serious problem because we are no longer adding a cup of ethanol to an entire tank of pure gasoline to stabilize it but we now have a gallon of that ethanol crap for every 9 gallons of gas in the tank and at that level it ATTRACTS moisture and causes gumming and crud and a pile of problems. So the question is, "Should we use 'fuel stabilizer' these days if we now have ethanol already in the fuel?". The answer is yes but not for the reason we used to use stabilizer that was to absorb water. Now we need it to combat all of the gunk and gumming this ethanol crap creates. So, you can use STA-BIL but today it is nothing more than cleaning solvents to fight the gumming. Its red form is the common form and the green marine form simply doubles the amount of cleaning solvents because ethanol gas used in boats tends to sit longer than gas in car so the added cleaning it provides is better. However, the recommended amounts of STA-BIL to use are quite low because years ago STA-BIL couldn't come out and tell people they now had to use more then they did in the past. So, long story short, if one is going to store their car with ethanol blended fuel in it I say don't screw around with STA-BIL. Put an entire bottle of Sea Foam in the tank (the whole 16 ounces), top it off with gas, drive it around for a while to get it through and system and then forget about it. You'll be getting way more protection due to the amount of cleaning agents you are adding compared to a few squirts of STA-BIL. Sea Foam blows away every other brand of fuel system cleaner on the shelf and has for decades... Everything else is garbage and a waste of $ in my opinion. Just my 2 cents.

The above being said, if I were to park my XF knowing I wouldn't be driving it for over a year, I would run the tank to almost empty (E on the gauge without running out of gas), add (2) 16 oz. cans of Sea Foam and then fill the tank with 100% pure gasoline (if you have stations that sell it in your area) until the pump cuts off. At that point the tank is full and the fuel has started up the fill pipe creating back pressure that cuts the flow off automatically at the handle . Drive it straight home and park it. You get virtually no water condensing in a tank that is full and you don't have that ethanol crap gas sitting in there for an overly extended period.