Definitive answer to best gearbox and rear diff oils...

[neckarsulm]

Going to drop my oils today while car is having a thorough going over.
I have searched long and hard for oils info and can't get the same answer from anywhere! I am not near Opie and need the oil today ideally.

So far I know the following;

MRC use OE spec, nothing fancy and I'll go with that.

I am pretty sure 75/90 GL 4/5 is good for the 'box e.g. from GSF;
98048A FUCHS TITAN SYN GEAR OIL 75W-90 4 L L4/GL5 SPEC) 15.50

Where I am confused is what to put in the diff? On the forums people say the diff oil is different to 'box oil and that GL5 should be used but isn't GL4/5 just as good? The only difference I can find between GL4 and GL5 is that GL5 can corrode syncros on older cars at really high temps.

In a nutshell do MRC use the same in diff and box?
And if not what spec do they use?

Thanks!

[supersi]

id just PM Doug or call mrc as there tell you ... top blokes at mrc

[neckarsulm]

id just PM Doug or call mrc as there tell you ... top blokes at mrc

I'd feel bad asking Doug and then doing it myself.
I'll get someone else to ask him (joke)

[juice]

Hi mate, i used the exact same oil in my gearbox that you searched fromGSF

however in my diff i used silkoline sil tran syn 5 and i think its 75w- 90.

[neckarsulm]

Thanks Juice.
Did you deliberately choose different oils or just do them at different times?
They are both 75/90, look similar spec GL4, GL5 but Silkolene is fully synthetic
Both made by Fuchs!

[juice]

nope, both done at same time, spoke to opie oils who recommended the titan gear oil for the gearbox and the silk tran syn 5 for the diff (fully syn)

speak to guy at opie, he'll probably advise same stuff

[Nige_RS4]

nope, both done at same time, spoke to opie oils who recommended the titan gear oil for the gearbox and the silk tran syn 5 for the diff (fully syn)

speak to guy at opie, he'll probably advise same stuff

I went for their recommendation and found that 1st to 2nd became much notchier when cold, so I ended up putting the OEM stuff back in.