With the engine running check the voltage at the battery post with a volt meter. You should have from 13.5 −16 volts. Any less and the alternator is bad.
12 volts
10 volts minimum,18 max.
On a 2002 Mercury Sable : Each wheel has ( 5 ) lugnuts / total of 20
No less then 13.8 and no more then 14.2 Volts with engine running.
According to the 2002 Mercury Sable Owner Guide : ( 18.0 U.S. gallons )
There are two.
Look under the vehicle and count them.
A Mercury Mountaineer can get up to 14 miles to the gallon. This all depends on what road your traveling on.
According to the 2002 Mercury Sable Owner Guide : For all trim levels ( 18.0 U.S. gallons )
369k and still starts up no problem
the four door speakers are 6x8 and the sob if you have one is 8"
There are many vacuum hoses, consult a repair manual.