Just acquired my first MX-5 and want to change all fluids.
Have read all about how to and what to put in etc…Is it worth adding some of this (link below) into the gearbox and diff, or just gearbox only, or not worth it.
Only considering it as it’s recommended on the Vx forum to go in a vectra gearbox to improve the gear change, after an oil change of course.
Cheers
Mick
Use a good quality oil, Mazda recommened a grade of oil in the car handbook and do not then advise you to add Moly. They just advise an oil.
As above really, dont bother with any additives. Just use a good quality oil.
Cheers
Guy
Many years ago I emailed Redline oils thus
Sent: 16 May 2001 00:48
To: Geoff Walton
Subject: Re: Lubricants
>Hi
>Can you please tell me which lubricants you recommend for fast road use
>in the Engine, Gearbox and Rear Axle in my 1990 Mazda Eunos Roadster
>(Miata in the USA) ?
>Regards
>Geoff Walton
In your Mazda, I would recommend the Red Line 10W30 in the engine,
the MT-90 in the transmission
and 75W90 in the differential.
So general opinion is, just change the oil no additive is really required.
Mick
Yes
eddie
A synchromesh gearbox, like wot we got, relies on a certain amount of friction within the synchro-cones and baulk-rings in order to help the operation during gear-changes, Lucas oils do a gearbox additive but what do the Americans know about manual gearboxes (or anything else really)?
Just use a good oil, clean all the metal off the magnetic plug and enjoy
on 1.8s remember to check the oil in the remote shifter and add up to 50cc if needed (from inside car)
Dr Eunos 
The 1.6, Mk2.5, has the oil in the top of the gearbox also.
I can’t recommend Redline MT90 highly enough, it really smoothed out the gear changes in my mk2.5 1.6.
Yep 