Diff Fluid Change With Castrol Syntrax 75W-90

Only 21,761 since the last diff fluid flush I felt it was time to do it again. This time I decided not to continue with Mobil 1 75W-90 synthetic but instead Castrol Syntrax 75W-90.


Because I felt a faint whine on a recent trip down the shore which was a bit unsettling. It was too soon to flush the fluid. If I understand it correctly the interval should be 30k miles, but as you can see in my case I fell way short. And I’m glad I did flush it because the Mobil 1 gear oil that came out was fairly dark!

Lots of sludge on the magnetic bottom nut of the rear diff. And a very dark oil in the catch can after the flush. Hoping this Castrol last longer than Mobil 1 did. But if not, it’s a cheap enough maintenance item to do as frequently as is needed.

Original blog post: click here.

Motorsport Marshal, Miata Driver, Hot Wheels Collector