I’m trawling through the Eurocarparts website and am considering buying gearbox and differential oil from there. I’ve seen the statement that GL5 oil is good for the diff and GL4 is good for gearbox, both being around the 75w90 or 80w90 viscosities.
I’m considering the Triple QX 80w90 oils for this application, though the LS variant for the slip-diff. Would these do a suitable job or is it better to source these elsewhere?
Here is the link for the non-LS derivative.
Here is the link for the LS derivative.
Atop this, is the K&N Filter, –> Here <–, suitable for the Mk3 MX5?
Finally, it seems to be about the cheapest place to get Mobil 1 fully syn 0w40, after the father’s day discount is applied, just to let you all know!
Personally I would go for this for the gearbox
http://www.opieoils.co.uk/p-739-castrol-syntrans-multivehicle-75w-90-fully-synthetic-car-gearbox-oil.aspx
This for the diff
http://www.opieoils.co.uk/pv-964-castrol-universal-75w-90-semi-synthetic-car-gearbox-oil-1-litre.aspx?gclid=CICQqfz6wdQCFe4y0wodrSwMwQ
And this for the engine
http://www.opieoils.co.uk/search/go?w=mobil%20super%203000%20x1%20fe%205w-30
You may find Halfords will be cheaper on the Mobil oil, that’s using the OC members discount (if allowed to access it) Halfords don’t seem to carry the Castrol oil above anymore, hence the link to Opie.
Also if going for the oil filter, get a genuine Mazda one.
All these suggestions of course are my personal choices and what I use on my various Mx5’s, whatever you use just make sure it meets the requirements.
BTW those oils you mention do seem to be of the correct grade/spec for your car.
Eurocarparts list a 75-90 fully synthetic gear oil, which I used in my car. I wouldn’t pay the premium for a filter just because it says K&N - completely personal opinion.
Spec for your car is a 5W-30 or alternatively a 0W-30 is fine. No benefit in going to a 40. In fact a technical downside.
JS
Thanks both. I think the engine oil is a decent price after discount - if they’ve a cheaper 5w30 then that might be a more cost-effective option but either way it’s probably not a huge difference in the grand scheme of things.
The engine oil side of things is pretty straight forward, in my opinion, but the gearbox and differential oils are where I find myself in muddy waters. Is there any benefit of semi-synthetic vs fully synthetic in this scenario?
I went for the K&N over OEM purely because it’s inexpensive and available for collection from ECP - I’ve just had a look and they do the Castrol 3000 5w30 for £30.55 after discount is applied, which is absolutely fine in my opinion. I think I’ll stick with that because it’s OEM spec as JS has stated! 
All I need to do now is choose which gearbox/diff oils are suitable and purchase those and I’ll be good to go.
Thanks once again for your help guys, I’m getting there in terms of servicing! A skill worth it’s weight in gold!
Just for information Mobil Super 3000x1 Fully Synthetic 5W30 5L at Wilko’s for £24.00p. Don’t know if this is of any use to anyone.
Why yes it is. Thanks to you sir, I think I will order it to my local store and pick some up Monday! ![]()
Let us know how you get on with the oil changes, please.
I picked up the oils from opine but still have to find the motivation to crawl under and do them…