You don’t need this additive unless you have a near worn out engine.
Mike is exactly right about STP and cold winter days. It’s going to work the battery and the starter motor much harder; if it starts at all.
Many years ago I worked for a small town Subaru dealer. Subaru at one time required, and paid for, an manual transmission oil change at the 1000 miles mark along with several other little chores.
Our sorely lacking service manager INSISTED that every trans oil change (they used 80/90W hypoid oil) also get a can of STP oil treatment with it.
You can just imagine what shifting a transmission was like on a zero degree day, much less a 15 below one, with STP diluted 90 Weight gear oil.
The best analogy would be rowing a boat through a tar pit.
One could even notice it when the car was decelerating since it gave the feeling that the brakes were half-applied.