Which gearbox oil to use for a series 2 nb

[Cooney]

Hey guys,

Bought my first mx5 the other day, so I'm new to the forum.

I've read around a bit and seen that others have had the same slight 'crunch' when changing between first, second and third, and suspect it may be a worn synchro.

I figure it wouldn't hurt to change the gearbox oil, so popped down to sca today. I've read that I should be using GL-4 SAE 75W-90 oil, but they only stocked either GL-4 SAE 75W-85 or GL-5 SAE 75W-90. So I'm wondering what other people have used in the past and what's worked best, is there a preferred brand? Also whether you'd recommend full or semi synthetic.

Cheers

[TIP]

redline 75w 90 not sure which gla

[Mr Morlock]

It's been covered countess times. The point that needs to be understood is that there is no perfect manual transmission as far as gearchanging is concerned. Technique- you do not just rush changes from 1st to 2nd - its usually when the oil is cold so you ease it thru the change. My own car( NBP2) just runs a standard spec oil and I find the 1-2nd change ok and the rest of the changes better- but thats normal. An analogy If you have an injury medication may cause further damage ie by masking pain and rushing changes 1-2nd may also cause damage to synchro rings. When synchros are worn by drivers having no sympathy with the manual change then a mechanical repair maybe necessary. If this just all sounds like a load of codswallop by all means go and talk to some older mechanics or enthusiasts - people who have had years of experience in driving manual cars ( Doc would know) . Today many drivers either never drive manuals or only drive them occasionally and some drive them poorly.
The owners manual will tell you the spec of the oil required.

[93_Clubman]

To answer OP's question, good results for forumites from Nulon full synthetic 75W-90:
http://www.nulon.com.au/products/Gear_a ... a_kZ5w2X_g

& some forumites are also adding this Nulon additive:
http://www.nulon.com.au/products/Specia ... Treatment/

Discussion here:
viewtopic.php?f=29&t=58426

[JBT]

You need GL-4. Your gearbox (synchros in particular) may suffer premature wear using GL-5. See this http://wiki.answers.com/Q/Whats_the_difference_between_gl4_and_gl5_gear_oils and this http://www.theoildoctor.com/store.asp?pid=36382 for some background info.

Out of interest, the recommended spec for the NC gearbox is GL-4 SAE 75W-90 and GL-5 SAE 90 is recommended for the differential.

Some oil manufacturers have oils that they claim will be OK in GL-4 or GL-5 applications - such as Penrite Transgear 75W-90 http://www.penriteoil.com.au/products.php?id_categ=4&id_products=380

[project.r.racing]

You need GL-4. Your gearbox (synchros in particular) may suffer premature wear using GL-5. See this http://wiki.answers.com/Q/Whats_the_difference_between_gl4_and_gl5_gear_oils and this http://www.theoildoctor.com/store.asp?pid=36382 for some background info.

Out of interest, the recommended spec for the NC gearbox is GL-4 SAE 75W-90 and GL-5 SAE 90 is recommended for the differential.

Some oil manufacturers have oils that they claim will be OK in GL-4 or GL-5 applications - such as Penrite Transgear 75W-90 http://www.penriteoil.com.au/products.php?id_categ=4&id_products=380

GL-4 is fine as long as the oil also has a military spec.

Go to the specs of any bottle or oil manufacturers website and have a look at the specs. If it is GL-5 and also has something like MIL-XXXXXXXXD or E in the specs. It is fine to use on brass synchos as it has additives to protect the brass.

[speed freak]

I have a NB8b which Iv recently purchased. In my owners manual for the gearbox oil it states either GL-4 or GL-5 75w-90 and for the diff it states GL-5 SAE 90.

Any of the good brands will be fine (just dont use homebrand oil) main thing is getting the right thickness.

Since I just got my car Im not sure when the oils got changed last so Iv just decided on brands and the oil I want and recently bought all mine to replace.

I ended up going Royal Purple for the gearbox (because Ill be using mine for track days as well as daily) and a semi synthetic Nulon for the diff.

Nulon, Castrol, Penrite, Royal Purple and Redline all seem to be popular. Some say Redline fixes the 1st to second crunch but others say it done absolutely nothing to help. I wouldnt worry about it though from what I read all 6 speed NB gearboxes do this so it shouldnt be much of an issue. Just try and take it slow when its cold.

[Cooney]

Thanks for all of the replies guys. I'll definitely stick to GL-4 to prevent any further wear to the synchros. I found out today that repco stocks the oil (surprised sca don't) so ill grab some during the week.

And by the sounds of it I think I'll go with fully synthetic, unless anyone would recommend otherwise?

Cheers

[Aussie Stig]

To answer OP's question, good results for forumites from Nulon full synthetic 75W-90:
http://www.nulon.com.au/products/Gear_a ... a_kZ5w2X_g

& some forumites are also adding this Nulon additive:
http://www.nulon.com.au/products/Specia ... Treatment/

Discussion here:
http://mx5cartalk.com/forum/viewtopic.php?f=29&t=58426

The first link shows that the Nulon is a GL-5 possibly not suitable.

[93_Clubman]

The first link shows that the Nulon is a GL-5 possibly not suitable.

Which gearbox oil to use for a series 2 nb

I have a NB8b which Iv recently purchased. In my owners manual for the gearbox oil it states either GL-4 or GL-5 75w-90 and for the diff it states GL-5 SAE 90.

[Okibi]

I liked Redline MT90 in my 5 speed, think i'll try it on the 6 speed as well.

[Aussie Stig]

The first link shows that the Nulon is a GL-5 possibly not suitable.

Which gearbox oil to use for a series 2 nb

I have a NB8b which Iv recently purchased. In my owners manual for the gearbox oil it states either GL-4 or GL-5 75w-90 and for the diff it states GL-5 SAE 90.

Some people like Royal Purple (maybe for the colour) others Redline and others Motorcraft.
I don't think there is one answer for the 6 speed.

Dunno about GL-5 though (& I quote).......

while the Mobil 1 gear oil meets the specs, for the 6spd it is a very poor choice. while the GL-5 oil is part of the specs that mazda puts out on the aisin transmission, the EP additives in the GL-5 make it a poor shifting oil, fouling the syncros and promoting notchy shifts. there is no fashion that this will do any harm in the 6spd, but it just doesn't do the job right, at least for me.

the Motorcraft lube is a GL4, with friction modifiers, in a 75w-90. the MTL is thinner than the spec, and the GM Syncromesh is thinner than spec(although i have heard of no problems with people using it).

i am a big Mobil fan, but this is an area that they fall flat on. now, the 5spds will digest the M1 just fine, but the 6spds are really finicky.

I guess you take your chances.

[93_Clubman]

The first link shows that the Nulon is a GL-5 possibly not suitable.

Which gearbox oil to use for a series 2 nb

I have a NB8b which Iv recently purchased. In my owners manual for the gearbox oil it states either GL-4 or GL-5 75w-90 and for the diff it states GL-5 SAE 90.

Dunno about GL-5 though (& I quote).......

while the Mobil 1 gear oil meets the specs, for the 6spd it is a very poor choice. while the GL-5 oil is part of the specs that mazda puts out on the aisin transmission, the EP additives in the GL-5 make it a poor shifting oil, fouling the syncros and promoting notchy shifts. there is no fashion that this will do any harm in the 6spd, but it just doesn't do the job right, at least for me.

Sounds like it might be just a punters thoughts based on his/ her perception of some experience. And without a reference, it's just another quote, & as we know you can find someone, somewhere that says anything you want to support a issue, such is the nature of information.

Personally, I favour deviant's extensive MX5 experience, as well as his specific experience with Nulon in his NB8B:

I use this and it works for both road and track: http://www.nulon.com.au/products/Gear_a ... a_kZ5w2X_g

viewtopic.php?f=29&t=58426

[Aussie Stig]

I take your point, anything on the interwebs, needs to be filtered, however credilble sounding.
However this is not the first GL4 > GL5 opinion for the six speed.

Unfortunately Deviant is just one happy punter, statistically worthless unless corroborated.
Unless I am reading wrong, his comment reflects my experience with the stock oil, not a huge recommendation.

"My NB8B is not great when it is cold, it goes in to gear okay but has more resistance than when it is hot."

Take your chances - suck it and see.

[93_Clubman]

However this is not the first GL4 > GL5 opinion for the six speed.
Unfortunately Deviant is just one happy punter, statistically worthless unless corroborated.

And his is not the first favourable opinion for the Nulon.