Mixing gear oil

Mikead40

Mikead40

New member
I need to change out my rear diff fluid. Laying around my garage I have a quart of amsoil, a quart of royal purple and about half a quart of castrol synthetic. All are 75w-90. Is it ok to mix these?
 
AJK

AJK

New member
Your ok to mix. You would just de-rate all other oils to the lowest of the three brands. Also make sure all have the right friction modifier for your diff.
 
Mikead40

Mikead40

New member
AJK said:
Your ok to mix. You would just de-rate all other oils to the lowest of the three brands. Also make sure all have the right friction modifier for your diff.
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Thank you for your response - when you say de-rate, what exactly do you mean? I'm assuming the API GL rating - in which case all are meet GL-5 requirements based on their data sheets
 
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David1tontj

David1tontj

New member
Mikead40 said:
Thank you for your response - when you say de-rate, what exactly do you mean? I'm assuming the API GL rating - in which case all are meet GL-5 requirements based on their data sheets
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I think that's what he meant. Basically just treat your new oil as if it's the worst of the 3.
 
AJK

AJK

New member
David1tontj said:
I think that's what he meant. Basically just treat your new oil as if it's the worst of the 3.
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Exactly, change intervals and friction modifiers are different in all three. Castrol being the worst of the three. So just treat all the others as if they were Castrol.
 
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TomJK

TomJK

New member
AJK said:
Exactly, change intervals and friction modifiers are different in all three. Castrol being the worst of the three. So just treat all the others as if they were Castrol.
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Castrol is the worst? Aw man... I just put it in my read dif, and was going to put the rest in the front... Is it really that bad?
 
AJK

AJK

New member
TomJK said:
Castrol is the worst? Aw man... I just put it in my read dif, and was going to put the rest in the front... Is it really that bad?
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It's ok stuff, just the lesser of the three brands listed.
 
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