Afternoon all, I’m wondering if anyone can give me a any recommendations from experience about which is the best gearbox oil to really complement the 5 speed box in a MK3 NC… I’m torn between these two: https://www.opieoils.co.uk/p-739-castrol-syntrans-multivehicle-75w-90-fully-synthetic-car-gear…

I said this in my two posts in this thread re the Redline, it mentions the Syntrans and which diff oil I used. [image] Red line revelation! Engine, Transmission, Exhaust etc

Buuuuutttt… You’ve got the 6 speed box which are famous for being notchy and a hot awkward, particularly when cold… The change on mine is really quite nice so I just want to change it for the piece of mind more than anything, but at the same time I’ve changed transmission oils in the past and had …

The Syntrans is suitable for the 5 speed even though that doesn’t display the 1st to 2nd notchy change. I’ve used it in my Mk1 5 speed, all good. As long as it says GL4 on the label it’s good. As they say here, suits all model although Mobil it’s GL4 spec. https://www.mx5parts.co.uk/gearbox-manua…

Funnily enough, there’s one review of that oil on the mx5 parts website and someone is complaining of a stiff change when cold, citing the GL5 standard vs recommended GL4 standard as being the culprit

Having said that, my user manual specifies either GL4 or GL5… Do you know what the difference is between them? Is GL a durability or viscosity indicator?

Explanation here… [image] The difference between GL-4 and GL-5 explained - Rymax Lubricants When you are choosing a transmission or gear oil you might be wondering what GL-4 and GL-5 mean and what the differences are between these two classifications. Choosing the right classification is …

You are probably over thinking this. For a box that you say has no shifting issues the safe bet is somethinglike syntrans with GL-4 spec. GL-5 oils generally have an extreme pressure additive package based on Sulphur compounds which are thought to cause damage to brass components.

Just an opinion, but it’s best to ask what is the “Correct Oil”. To which (as already pointed out) are many. As long as you choose the “Correct Oil” you should have no problems. Brand is generally a personal preference. I recently have used Total, but that’s just me. If opie oils comply and is …

[image] ChrisMK3: Funnily enough, there’s one review of that oil on the mx5 parts website and someone is complaining of a stiff change when cold, citing the GL5 standard vs recommended GL4 standard as being the culprit That’s a bit confusing, buyer claims they supplied GL5 but the blurb on ac…

That’s a good tip and advice too! :+1:

Best gearbox oil?

Technical Area Engine, Transmission, Exhaust etc

MickAP 25 May 2020 17:07 8

Explanation here…

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