For GL 5 suitable for use where oil to GL 4 is required too. I wouldn’t use it in the gearbox, diff yes.
I appreciate that you would not use it but it does state ‘Recommended for use in applications requiring–API GL-4’.
Recommended by the people selling the oil… 
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Indeed, but I was commenting on the above.
Which in the UK, is as elusive as Mazda’s own IS long life gear oil.
What might be easier for a user going that path, is the Castrol Transmax 75W-90 GL4, given it says on the spec sheet (and bottle) ‘Ford WSD-M2C200-C, MB-Approval 235.72’
source: Castrol Classic Oils Shop — Buy Castrol Multivehicle 75w90 - manual transmission oil
As if on one looks at the actual spec sheet of the Motorcraft XT-M5-QS, it has a specification number WSD-M2C200-C, i.e, the same as the Castrol one above
source: https://www.motorcraft.com/us/en_us/home/our-products/chemicals-and-lubricants/transmission-fluid/full-synthetic-manual-transmission-fluids.html
Not also though, the Mazda IS long life gear oil ISN’T 75W-90, but 75W-80, as discovered by my own communication with Mazda UK, when I questioned a part number they gavve me was for 75W-80, given in the manual if says 75W-90 (GL4) can be used if the Mazda long life gear oil IS cant be obtained.
This was my response from Mazda (one of a chain of emails):
'Good afternoon
Thanks for your response.
I can confirm the vehicle should have 75W-80, however, if you cannot obtain 75W-80 then 75W-90 can be used.’
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By coincidence, the Castrol Transmax was exactly what I’d ordered from Opie after hunting for a GL4 in the correct viscosity.
The difference has been fantastic from the off. The gearbox has now had a good flush with a couple of other types of oil but this Castrol seems to be the stuff. Even the blurb states “Used successfully as a problem solver for low temperature shiftability issues and in the manual transmissions of a number of manufacturers as factory fill”.
The car currently being used on a 100 mile run so will report back on hot performance (as hot as it could get on a wet day like today!)
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Further update now some 500+ miles done is that the Castrol Transmax seems to work very well. Still a tiny bit of notchiness in 1st/2nd but generally very smooth changes now.
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Hat tip to someone reporting back with updates after use
Difficult to say as the car is new to me but the change has seemed to improve since change to Transmax. Not heaven & earth sort of thingy but just more comfortable with the change quality.
Equally could be wishful thinking!
‘06/5sp/48k
Just ordered the Castrol stuff off ebay Opie as cheaper than Opie direct, weirdly. Not by much but also got bored of trying to put addresses in and details on Opies site. Not that the car will notice but now have the diff oil ( Motul) , which I used on a diff in a Westfield which was the same one as these and gearbox oil ( castrol) to now get swopped out , as sure it hasnt been done looking at the drain plugs and corrosion lines around them.
I pick up direct from their depot. On the one occasion eBay was cheaper they gave me that price without me asking.