You don't say which model year of Mercury Mountaineer but they have all
used the ( BCI group size 65 battery ) such as the Motorcraft BXT-65-650
Cranking battery.
Mercury 1984 6 cylinder L6 what type & size of starting battery is required
a car battery made for that vehicle
r134a
Watch Battery #371
A mercury battery will provide constant voltage. A voltage regulator circuit will also.
SAE 5w20 any major brand.
Regular unleaded , 87 octane
Hey should have a number on the battery, type that number in on google And a picture should show up.
button cell cr2025
The old battery should have the type written on the label under all the crud that has built up over the years.
mine has a sony SR626SW