Any major brand of SAE 5w30 conventional or synthetic.
DOT 3 brake 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.
It will usually tell you on the transmission's dip stick handle but I also have a98 Mountaineer AWD V-8 and it uses Mercon V
According to the 2001 Mercury Mountaineer Owner Guide : For the 4.0 litre SOHC , v6 engine and the 5.0 litre V8 engine ( " regular " unleaded gasoline , 87 octane )
Start with 6qts but be prepared for it to take 7qts
Motorcraft MERCON - V , automatic transmission fluid in the automatic transmissions
On a 1998 Mercury Mountaineer : Using a funnel , add the automatic transmission fluid through the automatic transmission fluid dipstick tube . It is located near the firewall , just to the right side ( passenger side ) of the engine , where the transmission is bolted to the rear of the engine . ( the type of transmission fluid to use should be engraved into the dipstick )
134a
According to the 2000 Mercury Mountaineer Owner Guide : With engine oil filter change : Both the 4.0L SOHC V6 and the 5.0L V8 engines take : ( 5.0 U.S. quarts of 5W-30 )
On a 2002 Mercury Mountaineer : ( DOT 3 brake fluid meeting Ford specification ESA-M6C25-A ) According to the Owner Guide
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 , if that is what you are asking ?