Hello,

I am trying to see which rear diff oil would fit in my STR from 2004, but the main issue is now that I either have to pay 50€ for a bottle of 1L of Ford Rear Diff Oil 75W-140 meeting spec WSL-M2C192-A or, 18€ the bottle of Castrol Syntrax Limited Slip Differential Oil 75W-140 (Formerly SAF-XJ 75W-140) which is ment for LSD but aparently it can be used in open diffs lik the STR main issue is that it meets no Ford or STJL specs it's just (ZF TE-ML 12D, ZF TE-ML 16G, ZF TE-ML 18, ZF TE-ML 21C, MB 235.61, ZF TE-ML 05C)

Mind me that I want to change the Rear Diff oil because it's the original one it has the left the factory with (20 years old oil lmao) and by doing that I might prolong the life of the rear diff it has no issues or makes any weird sounds but if I am planning on changing all brake discs and pads why not do the rear diff and especially try and fix my park brake (the cables or motor are gone)

Will it be ok if I fill up my rear diff with Castrol?

Thank you!

 

Yes, you definitely should change the oil diff. I have the V6 but indeed they both use the same 192-A spec.

There should be no problem with adding a generic 75W-140. An example of this would be the MOTUL GEAR COMPETITION 75W-140, or that Castrol you indicated.

However, I am very picky and since this oil will last at least another decade, I complied with the spec. I specifically bought Liqui Moly Hypoid GL5 LS 4421, at 32 euro per litre.

Your choice.

 

Thank you for the kind reply, I will use this Castrol for now and at the next change I will go for Liqui Moly.

 

I like Mobil1 products and use their 75W-140 synthetic fluid and motor oil. I also found an easy way to get the old fluid out too. There is no drain plug. I got a little fluid pumper and a 12" piece of 3/8" copper tubing bent to 90 degrees over a piece of 4" pipe to get a nice curve to it. You then put the tubing in the end of the flexible hose and you can put the tubing down to the bottom of the dif and get almost all the old fluid out. Good luck doing that with the flexible hose, just put the tubing on the output end of the pump to refill it.