To clarify, do those with experience reckon using Millers 75/140 crx NT+ fully synthetic in both gearbox and diff is a good idea please?
It’s a GL4/5 classification, and is suitable for LSD.
I appreciate the gear shift quality when cold may be compromised a little, but rarely do short runs, so I can live with that.
The diff on my car is quite noisy, when doing a 3 point turn (for example) but no whining noises, so I guess it’s the clutch packs and normal.
I want to minimise the chance of problems with either box or diff, and welcome input from anyone with some knowledge .
Cheers.
I just changed mine and used the Mazda approved hypoid oil in the LSD.
Not done the gearbox yet.
Diff takes 0.8 litre, drain and fill plugs are 23 and 24mm.
Recommended a syringe pump to refill as it’s difficult to get a bottle high enough to squeeze it in. https://www.mx5parts.co.uk/diff-genuine-mazda-long-life-hypoid-mk4-p-4571.html
As far as I know the gearbox takes 75w/90 GL4 spec. I don’t think it’s recommended to use GL5 as that is different spec.
I use the 75w/140 in my gearbox, it is slightly stiffer for the first couple of minutes but slightly smoother than the Mazda oil thereafter. I stick to 75w/90 for the diff but change it annually regardless of mileage (which for me is very low)
I use Miller’s CRX 75W/140 and as Gareth says there is a bit of stiffness in gears 1 and 2 when cold but the gearbox is smoother when hot, a small price to pay for hopefully longer life. However gearbox life is improved on the ND2 due to the DMF and engine tuning but certainly worthwhile using the Millers oil as the gearbox problems still exists. I also use the LS version in the differential.
I have bought some of this oil CRX 75W/140 NT+ but Millers technical department did not really recommend it as they said it was too viscous and recommended the CRX 75W/90 NT+ as it is the same viscosity as the OEM oil. They may just be protecting themselves. What they could not tell me for either oil is the “drain time” which I take it is the life of the oil. Do you change the oil in your gearbox regularly or is it in for “life” like the OEM oil? If you do change the oil regularly, how often do you do this? Same questions for the LS oil you use in your diff also?
I have used 75w/140 in the gearbox for over 4 years with no problem. It’s a fully synthetic oil which is needed because the gearbox gets very hot. I use this oil because it was recommended to use this grade of oil by a gearbox specialist. This is to try and protect the gearbox due to the questionable build quality. Mine is a 2016 Recaro with the V1 version of the gearbox. However it can be a bit recalcitrant to select 1st and 2nd so for most people want their gear selection to work from cold so 75w/90 is ideal for them. I change the gearbox/differential oil every 2 years because both get very hot.and it’s cheap insurance. Oil analysis has shown that the Mazda oil cannot withstand the heat and degrades quickly…
I can understand that Miller’s would recommend CRX 75w/90 as they would be unaware of the gearbox problems.
As an alternative I used Motul, mainly because the one oil does both gearbox and LSD. It is similar in regards to what Chris has said, is a bit stiff when cold, although I find moving through the gearbox stationary before driving off helps.
Are we sure you can use the same oil? The diff is a ‘hypoid’ oil. I was under the impression the two were different as they did different jobs.
Just asking as this is first time I have seen GL5 for both applications.
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