Castrol 75w-90 Gear Oil - Is it any good?

[Mossyoakglock]

I need to change my rear diff fluid here soon and came across Castrol's 75w-90 gear oil. They didn't have it the last time I was in the store so I went with Mobil1. It meets or exceeds the GL-5 spec and is about $4 cheaper than the Mobil1.

Is the Castrol a good fluid or should I stick with M1?

I don't have any Amsoil dealers close to me so it's got to be something I can get in an autoparts store.

 

[fxrider]

Its Great oil, if it meets your specs go for it, the M1 is synthetic.

 

[Ursae_Majoris]

I have used it in my Axiom's rear differential for 30K. When I changed it, there was very little metal on the magnetic plugs. I was able to buy Valvoline cheaper, otherwise, I'd have gone with Castrol again.

 

[Mossyoakglock]

Is the Castrol not synthetic? I thought it was. I need a GL-5 rated synthetic oil.

If it's not then I can't use it since my truck calls for synthetic.

 

[Doug Hillary]

Hi,
Mossyoakglock - Castrol's synthetic gear lubricants are amongst the very best available. They have been long term players in the field (from the 1930-50s - well before BP took over) and many have their origin ex Germany

I have run comparison tests over many millions of Kms so I can "speak" with a lot of background knowledge

All my present vehicles have Castrol synthetics throughout their drivelines

Use with confidence - of course always use the correct specification for the application!

 

[Mossyoakglock]

Thanks, Doug.

Fxrider made it sound like it wasn't synthetic but I could have just read the post wrong.

I run Mobil in my engine but Castrol in tranny and transfer case so I'll probably run it in my rear diff to keep all drivetrain fluids the same.