[Healeys] Diff oil

[Peter Caldwell]

A further question on this topic.   Some older British vehicles had 
some brass parts in the diffs. I have heard there is a problem using 
a GL-5 specification for those applications. The current Castrol 
Hypoy C is GL-5.  I know that Redline makes a GL4 spec gear oil. Is 
brass or bronze content a consideration in Healey differentials?
         Peter C
--
At 02:05 PM 7/12/2012, Bob Spidell wrote:
>Everything I've seen/read/heard indicates you shouldn't mix oils of 
>differing viscosities, esp. multi-vis oils. The multi-vis oils are a 
>blend of base stock--e.g. 10W-40 has a base stock vis of 8 (I 
>think)--and various 'viscosity improvers' or VIs. The VIs are 
>polymers that start out as straight chains then sort of 'coil up' as 
>they get hot to thicken the base stock beyond what it would 
>otherwise be at a given temperature. I don't believe the effect is 
>linear--i.e. mixing 80W-90 and 85W-140 won't give a blend 
>proportional to the mixed quantities. Some say you shouldn't even 
>mix different brands of same viscosity, but I personally wouldn't 
>lose too much sleep over that. As an aside, you can mix grades of 
>gasoline to get differing octane ratings; in fact, I believe most 
>gas stations have just two tanks from which a third blend can be 
>mixed at the pumps.
>
>I don't think 85W-140 would hurt a Healey diff--it may even be 
>recommended in the manual, haven't looked in a while--it'll likely 
>be a similar base stock to 80W-90 with tons of VIs. The problem is 
>the VIs chains shear over time and the higher vis number goes down.
>
>Bob