No. It is the evaporative emissions service port (funny, that's what it says on the tag).
Look on the side of the accumulator can, on the firewall, under a ton of crap for the low side port.
If your original owner's manual is missing, download a soft copy from www.fleet.ford.com
under the MAINTENANCE tab.
1995 Mustang GT Convertible, only 68K miles.
200 Ford Contour Daily drive.
2001 F250 SD, 6.8L, 4 X4.
2007 Mercury Mariner AWD - Wifey's daily driver