According to the 2000 Mercury Mystique Owner Guide ( 5W-30 )
5W20 if it is the same motor they used in the 2001 it takes 6 quarts - should tell you on the cap unless it is a replacement cap !
5w30
Mercon V
5w30
5W-30 , according to the Owner Guide
" regular " unleaded , 87 octane ( according to the Owner Guide )
Use 5W30 in most cases.
Need to know if its 2 or 4 cycle.
idk what kind of motor is it. but based on what you gave me it's probably 1986-1988
SAE 5w20 any major brand conventional or synthetic oil.
The heater blower motor is on the interior passenger side. It is kind of a round shaped housing facing the floor.