Diff Oil Change

[Trickythemerc]

Just getting ready to change some fluids and in my stock of bits n pieces I have some Castrol Syntrax 75w140. Will this be ok in my diff or should I get some 75w90

 

[190]

75W140 is quite a bit thicker than 75W90

To put some numbers on it 75W90 being the first figure in each case:

At 0 deg C approx. 900 cSt vs 1600 cSt

At 40 Deg C approx. 100cSt vs 170 cSt

At 100 Deg C approx. 15 cSt vs 24 cSt ( it should never get this hot).


Is 75W90 the handbook recommendation ? some of the later cars are filled with a thinner 75W85 for fuel economy.

 

[Bellow]

If 75W90 is recommended, then stick to that. There is nothing to be gained by using an oil heavier than necessary - only losses.