Hi all, Could you please tell me where the filler/ level plug is on my 2010, 6 speed gearbox. I looked at the online manual and can’t find it anywhere. Cheers.
Looking under the car passenger side (left) the fill and drain plugs can be seen as in the diagram below. You may have a cranked aluminium cover plate to remove to access the gearbox, recently some members report they didn’t have any fitted on later models.
Do not mistake any look a like plugs as drain plugs on the other side (drivers side) of the gearbox, they need to stay firmly fixed in.
Does this help?
There is a good video on youtube also
2012 Mazda MX 5 miata NC Manual Transmission Fluid Change
By a poster called The After Work Garage
re-filling can be a challenge as there’s no room to get the squeezy bottle in.
I found it easier to extend the filler tube (I used an old home brew siphon tube), and elevate this inside the passenger door opening.
Also stand the new oil in a bucket of hot water for a while to make it easier to squeeze.
Have you ever tried one of those Machine Mart specials, the cylindrical syphon/pump😮
Ended up with more on the driveway than in the gearbox, they leak so badly.
I’ve never really found a route from the engine bay to the gearbox to feed a hose through on my Mk3, worked a treat on my Mk1/Mk2. Just taped a funnel on the end and pour away.
Big oil syringe, cost about a tenner from all your favourite retailers, takes about a pint on every squirt. Very useful to have around, used for gearboxes, diffs, flushing turrets, etc. Lasts for years.
great info above, thanks.
I have a question regarding the gearbox oil on a Mk2 1.8 6 speed - the previous owner swore by using semi synthetic engine oil in the gearbox rather than gearbox oil. does this sound logical, doesn’t to me, but he seemed like something of an enthusiast and had reams and reams of service and repair history and claimed it was something recommended on the various places he got his MX5 info from.
Any thoughts appreciated on the above topic.
Thanks,
Pete
No. And for a second opinion. God no.
Motorcycle gearboxes can share the same engine oil, but have all sorts of specific requirements, but your gearbox is meant to operate with significantly heavier oil than most motor oils. Also gear oil is designed to lubricate gears, motor oil has all sorts of other considerations build into it (such as heat tolerance, effect of burning, protection of catalyst etc).
Just no. Motor oil will work, but is not optimal.
Sorry to sit on the fence on this one 
I wouldn’t do it.
Sounds like he was using engine oil because it was cheaper, who knows
Need to ask the experts on this one but I think I already know the answer.
The classic Mini uses engine oil, it has to as the gearbox is in the sump, so it can work. But personally I would use ‘gear oil’ in a ‘normal’ gear box.
Thanks all - confirmed my thoughts. I will look into the stuff mentioned on other gearbox threads on hear. The chap seemed so sure of his gearbox “hack” that he was very convincing.
Gear oil contains “EP” extreme pressure additives to avoid metal-to-metal contact even with the high shear forces found in transmissions. The manual for my Mk.1 says its 5-speed gearbox takes GL-4 or GL-5 oil. An oil with no EP additives at all might be rated GL-1.
Fully synthetic engine oils can be expected to have higher shear resistance than ordinary oils but I can’t imagine where that previous owner got the idea that semi-synthetic was okay for gearboxes.
Just had a look through the paperwork he supplied with the car and 1 is the MX5 enthusiasts manual (similar to a Haynes manual). in there it states the GL4 or GL5 rating and a note saying something to the effect “these gearboxes respond well to synthetic oils…” which i believe means that they like synthetic gear oil but the previous owner may have interpreted it as regular engine synthetic.
Also, this manual only has the 5 speed box specs which state 2L as fill quantity - is this the same for 6 speed, or any difference?
Cheers,
Pete
GL-4 is recommended as some of the additives in GL-5 can be rough on the syncros
After a fair amount of work and advice from Total, I use this.
(Sure there are others that users use).
I specifically asked the questions about the syncro’s/soft metals.
I won’t bore you with the specification, but if it’s something you are interested in it is all on the Total web site. 
It is safe for the soft metal/s within the gearbox and I have no issues changing gear at all when cold.
TOTAL TRANSMISSION DUAL 9 FE 75W90 75W 90 MANUAL GEAR BOX OIL.
Yes, but recommended by whom? Mazda recommend GL-4 or GL-5.
I ran my first MX-5 on mostly GL-5 for a quarter million miles and the synchros were just fine when almost everything else on the car had been replaced or repaired. I know it’s probably the most regularly repeated saying about gear oil, that GL-5 can destroy yellow metal synchro rings, but is that current information or some sort of folk knowledge that dates back decades, like the warning that brake pads may contain asbestos or paint may contain lead?
On the mk3 I believe its not just yellow metals but other coatings added to the syncro rings.
Mazda make all manner of recommendations but I don’t believe they really care about 2nd or 3rd owners out of warranty. I don’t see what advantage GL-5 gives that outweighs the negatives.
Beautiful tool the oil syringe. Ideal for diffs as well. I’ve never regretted “borrowing” mine from a previous employer who doesn’t exist anymore. So I can’t take it back. 
Hi,
Thanks for the informative replies. I was wondering if anybody knew off the top of their heads what the fill amount is for the 6sp box on a 1.8 Mk 2?
Cheers,
Pete
