Use Ford part no. XO-5W20-QSP or equivalent motor oil meeting Ford specification WSS-M2C153-H.
Conventional or Synthetic your choice. I recommend Synthetic if the engine is sound and has no major oil leaks.
Hope This Helps.
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According to the ( 1999 ) Mercury Mountaineer Owner Guide :
With engine oil filter change :
The 4.0 liter V6 and the 5.0 liter V8 engines take :
4.7 liters / 5.0 U.S. quarts of ( 5W-30 )
( Helpfull )
Motorcraft MERCON V - automatic transmission fluid , according to the owners manual
In a 1997 Mercury Mountaineer : ( 4R70W )
According to the 2009 Mercury Mountaineer Owner Guide : ( Motorcraft MERCON-V automatic transmission fluid is used as the power steering fluid )
DOT 3 brake fluid
According to the 2009 Mercury Mountaineer Owner Guide : ( Motorcraft MERCON - V , automatic transmission fluid is used as the power steering fluid )
THE REFRIDGERANT USED IN A 98 MOUNTAINEER IS 134A. THAT INFO IS ON A STICKER UNDER THE HOOD THAT TELLS TYPE AND CHARGING CAPACITY.
The 5.0 litre / 302 cubic inch V8 used in a 1999 Mercury Mountaineer has a timing CHAIN
According to the 1999 Mercury Sable Owner Guide : ( 5W-30 )
Your 1997 Mercury Mountaineer came from the factory with ( Motorcraft MERCON automatic transmission fluid ) in your 4R70W automatic transmission ( the type that you are supposed to use should be engraved in your automatic transmission fluid dipstick just to confirm )
The best place to find a used Mercury Mountaineer is to check with the local garages and auction dealers in Syracuse, NY. They are bound to have the ideal vehicle for you.
Diesel Gas is used on the 2006 mountaineer
According to the 1997 Mercury Mountaineer owners manual : Your 4R70W automatic transmission takes ( Motorcraft MERCON automatic transmission fluid ) * the type that is used should be engraved into your automatic transmission fluid level dipstick *