diff oil spec?

[wellz13]

hi ive got a 1997 mk1 and just wondering what oil spec is recommened for the diff and gearbox?

cheers jon

[longdog_cymru]

Hi John, welcome to the forum

 

Use Fully Synthetic Mobil SHC 75W-90 in both your gearbox and diff.

But if you want the best, you can use RED LINE Synthetic Gear Oil 75W-90 GL5, pricey but good,

You can get both (and more) from here… http://www.opieoils.co.uk

[Razor_Blue]

@longdog_cymru

 Fully Synthetic Mobil SHC 75W-90 in both your gearbox and diff.

But if you want the best, you can use RED LINE Synthetic Gear Oil 75W-90 GL5, pricey but good,

My take on the question and above reply is somewhat different.

There is a general concensus that for older design gear boxes  it it better to stick to different types of oil for each application.

GL5 type oil is used for differentials and GL4 oil is used for gearboxes.  This is historically because of fears that the more aggressive additives in a GL5 oil will attack the brass/bronze synchro components in a gearbox.

In the newer “universal” oils such as Mobil SHC the additives are said to be chemically “buffered” so as not to attack brass/bronze. How effective this is I don’t know but there is no reason to use it since very good GL4 oils are available.

Mobil SHC like other “universal” oils is at the thick end of the 90 grade and is particularly thick when cold.  Mx -5 boxes are often reported as being difficult when cold and benefit from a thinner oil when cold (0°C).

Redline produce their much fabled MT90 GL4 75W-90 for manual gearboxes and indeed I have just changed my oil for MT90 to see if it improves my notchy gearbox.  So far the improvement is minimal, probably no more than any new oil would would feel. It’s early days yet as the new chemistry has not had time to bed down. However it’s certainly not magical and not I think worth the extra. It may have been exceptional when introduced  ~15years ago but others have now caught up.

So my recommendation is to save your money and use good fully/semi  synthetic oil that is readily available at your local Halfords etc

Differential —  Castrol  Syntrax Universal GL4/GL5

Gearbox -----  Castrol Syntrans Multivehicle GL4 75W-90 

Regards

R-b

 

 

[Rich_M]

Yes I used Mobil SHC in diff and gearbox 2 years ago. The diff is fine and it’s still in but the gearbox was awful so I swapped it out within a week for Syntrans GL4 and the shift is much better.

Bronze damage from GL5 is one consideration, viscosity of the actual oil is another, but the “slipperiness” is yet another. Synchro hubs are metal cone clutches which rely on being able to clear the oil in order to grab each other and sychronise the cogs in that fraction of a second of the first part of the gear selection before the cogs meet. GL4 oils are designed with this in mind whereas GL5 oils are designed to help hypoid axles cope with extreme pressure. Two different jobs.

Thanks for the update RB. I had an inkling of an idea to try Redline MTL next time, I know it’s a little lighter. Trying to remember when I last used it, about 15 years ago as you say in a Golf Mk3 I think, time flies

[MickAP]

@Razor Blue

@longdog_cymru

 Fully Synthetic Mobil SHC 75W-90 in both your gearbox and diff.

But if you want the best, you can use RED LINE Synthetic Gear Oil 75W-90 GL5, pricey but good,

My take on the question and above reply is somewhat different.

There is a general concensus that for older design gear boxes  it it better to stick to different types of oil for each application.

GL5 type oil is used for differentials and GL4 oil is used for gearboxes.  This is historically because of fears that the more aggressive additives in a GL5 oil will attack the brass/bronze synchro components in a gearbox.

In the newer “universal” oils such as Mobil SHC the additives are said to be chemically “buffered” so as not to attack brass/bronze. How effective this is I don’t know but there is no reason to use it since very good GL4 oils are available.

Mobil SHC like other “universal” oils is at the thick end of the 90 grade and is particularly thick when cold.  Mx -5 boxes are often reported as being difficult when cold and benefit from a thinner oil when cold (0°C).

Redline produce their much fabled MT90 GL4 75W-90 for manual gearboxes and indeed I have just changed my oil for MT90 to see if it improves my notchy gearbox.  So far the improvement is minimal, probably no more than any new oil would would feel. It’s early days yet as the new chemistry has not had time to bed down. However it’s certainly not magical and not I think worth the extra. It may have been exceptional when introduced  ~15years ago but others have now caught up.

So my recommendation is to save your money and use good fully/semi  synthetic oil that is readily available at your local Halfords etc

Differential —  Castrol  Syntrax Universal GL4/GL5

Gearbox -----  Castrol Syntrans Multivehicle GL4 75W-90 

Regards

R-b

 

 

 

The Castrol products mentioned above are the exact oils I have used in both my Mk1 and Mk2 gearbox and diffs. Do the turret oil as well whilst there, and maybe your shift boots for a completed job.