Transmission gear oil

[Joe912/62]

What oil is recommended for the manual transmission?
Can Synthetic be used.
Regards Joe

[peteracs]

Hi

You can use the the original recommended in the manual, but a number of us use Redline 75W90 NS, the NS is important....

Peter

[Joe912/62]

Non synthetic then?

[Joe912/62]

I can get 80W/90 GL-5

[peteracs]

This Redline according to their website is fully synthetic?

The important thing is that whatever you use does not attack the synchros.

Can you not get Redline?

Peter

[Joe912/62]

Would this be compatible?

[peteracs]

Hi

My personal view is that is for differentials and not for gearbox/diff combined. So I would not use it.

Can you not order online the Redline?

A quick Google brought up this comment re the NS and non NS versions of the Redline 75W90 which I think may help your decision making.

"Red Line 75W90 NS (Non-Slip) GL-5 gear oil is designed for manual transmissions and transaxles, using a high-friction, non-slip formula that aids synchro engagement for easier shifting. The standard 75W90 GL-5 contains friction modifiers, making it ideal for limited-slip differentials (LSD) but potentially too slippery for some manual synchros. "

Peter

[lancialulu]

For what it is worth back in the day extensive tests were carried out with various oils on Fulvia gearboxes that have the same brass sychro hubs. Mobil1 SHC 75-90 fully synthetic came out the best in terms of better shifting. I have used this now for 20 years in my Fulvias and not had unusual wear problems.

[Joe912/62]

Thank you for all your advice.

[rossocorsa]

I can get 80W/90 GL-5

GL5 used to be bad because the additives could corrode the brass components, part of the reason that Betas gained a reputation for a poor gear change. I've no idea if this still applies but I'd try to avoid it.

[Neil-yaj396]

For what it is worth back in the day extensive tests were carried out with various oils on Fulvia gearboxes that have the same brass sychro hubs. Mobil1 SHC 75-90 fully synthetic came out the best in terms of better shifting. I have used this now for 20 years in my Fulvias and not had unusual wear problems.

Heading for half the price of the Redline too! £60 of my 5 month old Redline ended up in the recycle tank at the garage doing the resto work on my Coupe 

[WestonE]

You must read the technical specification sheet for the oil and see "safe for Brass Syncho assemblies. Many GL5 75W 90 oils will attack the Porsche design Brass synchro assemblies our gearboxes use. I have seen what this looks like in a Montecarlo box and it is to be avoided. Note I am ex Oil Company Fuel & Lubricant division so I actually understand what all that technical jargon means most of the time and I do read it.   

[Joe912/62]

Thank you