5w30
Oil
The 1996 F150 owners manual shows SAE 5 W - 30 for the 5.8 L ( and SAE 10 W - 30 for the 4.9 L straight six and the 5.0 L V8 )
( 6 quarts ) WITH FILTER CHANGE
5W20 weight oil Answer came from Littlestown Lube & Brake in Littlestown PA 717-359-5022
According to the 1996 Mercury Grand Marquis Owner Guide : ( 5W-30 is the PREFERRED engine oil weight )
you can use 10w 30 or 10w40. doesnt matter that much. the weight relates to the thickness of the oil but you dont want it to thick because then it gums up.
It should be in the oil pan.
Consult the owners manual.
a 1996 F150 ,4.9 L ( 300 cubic inch ) straight 6 takes 6 quarts ( 5.7 liters ) WITH FILTER CHANGE
Should be on the side or rear of the oil pan
6 quarts ( 5.7 liters ) with engine oil filter change , according to the Owner Guide
5w-20 or 5w-30