I would like to replace the differential fluid on my 1990 300 sel. I plan on using redline. How many quarts will i need? Also is there any benefit to changing the power steering fluid to a synthetic? TIA

I always have at least two bottles
 

(those with the long pointed neck - 1 qt. each) when I do a diff. You will not be able to get all of the first bottle in it because of the angle. Pour as much out of it as you can then finish it off with the other bottle. Always remove the fill plug first.
Jim
'85 300D
'95 E320
'97 CRV

I bought a hand pump. I pump in the gear oil into the fill hole. The pump for gear oil may be available at place like Auto Zone and Pep Boys. I works very well with very little spillage.