It is a fuel filter. Therefore fuel must flow through this filter in order for it to filter the fuel. The fuel flows from the fuel tank to the engine, via fuel lines. Now, would you not figure that the fuel filter would be located somewhere between the tank and engine, along this line. Get down under the car and look for it. There is one exception. It is sometimes located inside the fuel tank with the pump. So, if you don't find it then it is in the tank.
In the front of the engine compartment , on the passenger side , inside the engine air filter housing
Find the filter which is under the car, There are special tools required which are cheap at the parts store. They should show you how to use them/
The computer module in a 2003 Mercury Mountaineer is located behind the rear right panel in the truck space. The rear right seat belt panel must be removed and then the lower panel. The module is located beneath a green plug.
Not by back passanger side tire. In front of the gas tank behind a heat shield.
I get 15.3 in my 2005.
According to the 2003 Mercury Mountaineer Owner Guide : ( DOT 3 brake fluid , meeting Ford specification ESA-M6C25-A )
That would be the 4.6 liter engine, which takes six quarts. * of 5W-20 according to the 2003 Mercury Mountaineer Owner Guide
Behind the drivers side rear quarter panel in the cargo area
( # 24 ) is a blue color 15 amp fuse for the cigarette lighter and OBD II in a 2003 Mercury Mountaineer ( under the instrument panel )
On a 2003 Mercury Mountaineer , 4.6 litre V8 engine : firewall 4 - 8 3 - 7 2 - 6 1 - 5 front of vehicle