- My model of MX-5 is: __2018 ND RF
- I’m based near: __SURREY
- I’m looking for technical help or recommendations on: __GEAR OIL
Hi all
Which gear oil should I use for changing in 5 year service
6 speed manual
Thanks
Kevin
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Interested in reply’s myself
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After consultations on here I used this Millers Oils Motorsport CRX 75w90 NT+ Fully Synthetic synth Gear Oil 5L | eBay
My observations are that the first few gear changes from cold are a little ‘sticky’. More so than the original oil. It ‘warms up’ within a mile and the change becomes slick. Once fully warm the change is faultless. (Note this gear box does not like to be ‘rushed’ even when hot and this oil does not change this).
I would recommend changing the differential oil as well, I used this Diff Oil, Genuine Mazda Long Life Hypoid SG1, 1 Ltr, Mk4 & RF – MX5 Parts
Don’t forget new sealing washers. (you could get away with reusing but buy in bulk and they are pence)
Plus, undo the filler first just to be on the safe side!!
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I’d recommend Millers CRX LS 75w/90 NT+ for the differential.
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Thanks gents, I am new to car servicing at this level… where is the diff? 
Thanks again
Kevin
Rear axle is the diff. 
I changed the gearbox oil on a 2018 ND and used “Mobil Mobilube 1 SHC 75W-90 Fully Synthetic High Performance Manual” bought from Opie (sure I saw it recommended here).
Now searching the forums for something else. The gearchange into 1st and 2nd is very notchy especially when cold. It gets better when warmed up but is still noticeable. The car has had a few 200 mile runs since the oil change and still it’s a pain to select 2nd.
Looking for an alternative oil now.
You want this below, it’s the GL 4 spec you want, you probably have GL 5, check the container.
BTW the GL 5 is ok for the diff.
Thanks Mick, I’ll get some of that and swap it over. Edited to say, the reviews for that product aren’t that good?
Be prepared for it to be no better. I have used the Millers gear box oil as recommended by others on here and it was slightly worse from cold than the original Mazda oil. It only takes half a mile to get it warm enough to work nicely and once warmed through the change is silky smooth.
The old saying ‘they all do that Sir’ is very applicable to this phenomena.
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Personally I’ve used in the past Castrol gear and diff oil, 75w 90, again GL4 for gearbox and 75w 90 GL4/GL5 (spec on the bottle) for the diff.
You can use the above for all models…
Gearbox x 2
Diff x 1
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I’m going to give the Millers a try. I have owned/maintained older cars (Triumph TR5 and original Fiat Panda) that needed GL4 or non sulphur oils and Millers was the go to oil. Will report back on how it compares.
Newport Mazda use the correct Mazda Long Life Gear Oil IS. I know because I saw it first hand, right in front of my eyes when I had mine done in April, 23. I was going to use Castrol Transmax GL-4 75W-90, as it seemed getting the Mazda juice was all but impossible. Even emailing Mazda UK and coming up short, save 20L drums, and someone in the US offering to ship it to me, but couldn’t due to customs (hazardous waste).
On the gearbox oil change day, they showed me what they ‘would’ use, just out of interest, if I didn’t use the Castrol (which I brought 3L with me), and my eyes popped out of my head when I saw the 20L drum of IS Mazda Original gear oil in front of me. Suffice to say I said put that in. I even supplied the workshop manual print out with all the torque values on, and I supplied the drain/fill crush washers.
Even driving from the first shift off it felt better (and it was good before).
I find them a nice bunch there and they go out of their way to ensure my laser needs are met. People often talk negatively about dealerships and not report good ones, but from my experience Newport Mazda have been great.
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Have been here myself with my 2016 nd
Originally changed gearbox with Motul 75 /90 & found cold shifting too notchy . Then after some searching Oxford Mazda sourced the ‘IS’ oil stated in the handbook, so have swapped out again & have to say cold shifting as smooth as warm & now happy.
As a side note as I recall this Mazda IS oil was labelled as hypoid which rang alarm bells … but when removing the outer label original IS gearoil labelling is revealed underneath.
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The Mazda oil is not the best to use in the gearbox. If the cold gear change is the most important aspect then use a fully synthetic 75w/80 oil. The gearboxes have a variable build quality so the use of a high quality oil is recommended.
There is that argument, granted.
However, if one’s gearbox is, touch wood, fine, and when they use the proper Mazda oil it’s like butter, it’s hard to go on a pipe dream trying different oils on the hope it’ll still shift as good and the ‘belief’ it’ll be better for its health, too.
You seem to have a belief that if the oil ensures a smooth gearchange everything is going to be ok. What about heat? Oil analysis has shown that the Mazda oil can’t withstand the heat generated in the gearbox. The diff too does get hot. All I’m pointing out is that there are better oils out there and if gear changing is your only criterion, then a fully synthetic 75w/80 will do it.
You could well be right regarding better quality oil as a 75/80 spec , not sure what grade Mazda IS would be ( presumably synthetic)
But this is a service change to fit & forget for 5 years for most , not something to repeatedly change out. Not sure the many recommendations on here for a branded 75/90 are helpful to a smooth cold change, it didn’t work for me!
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Why this obsession with cold gear change, I takes less than a mile to get some temperature into the oil so the 1st/2nd works.
It is no hardship to be a little patient, the world is not going to end because you can not get into second in less than a millisecond!!
No, I don’t think that, but I also think if it’s going to go it’s going to go. Heat wise, how hot it gets etc popping 12 miles over to ASDA I’m not sure. It’s more a case of I kept with what I’m happy with, as opposed to going with what random people on the internet suggest is better for me.