Castrol VMX-M 75W85 - why did we ever part ways ?

[Shannow]

Synthetic elitism ?

My Nissan was my first ever new car, and obviously wanted what's best for it, and synthetics since day one, and looked over my old "go to" for Japanese and French gearboxes that baulked going into 2nd when cold.

Never the smoothest of boxes in my Nissan (bit truck like and holds 5.1l of oil), the current synth had degraded such that first shift into second of the morning was half the time skipped to 1st/3rd.

VMX-M was on special over the weekend, so thought why not.

Loving it, best that the Navara's gearbox has ever been, including FF.

 

[zeng]

How would one explain the difference in performance?

 

[Shannow]

Not sure, but back in the day with our Holdens, we found that they were better on 1-2 shift with plain old GTX than most gear oils...

Dunno whether it's a genuine GL-4 additive rather than a half treat rate GL-5.

 

[supercity]

Originally Posted By: Shannow

Dunno whether it's a genuine GL-4 additive rather than a half treat rate GL-5.



I also use VMX-M in my car where the spec is 80w GL-4. I find there are good and bad days. Some days its like silk, others the first shift into 2nd just doesn't want to go. Overall an improvement on the Penrite Pro Gear 75w85 synthetic.
As you probably know the original application was for Mitsubishi FF. Just curious, what would you refer to as a genuine GL-4?

 

[zeng]

Originally Posted By: Shannow
Not sure, but back in the day with our Holdens, we found that they were better on 1-2 shift with plain old GTX than most gear oils...

Dunno whether it's a genuine GL-4 additive rather than a half treat rate GL-5.


It made sense to me to suggest that a proper GL4 in Castrol VMX M may have a more 'appropriate' Friction Modifiers for the manual synchros , as compared against a GL5 or GL4+ ...

 

[Ducman]

I am currently running the VXM-M in my old D21 Navara with good results even though it's a little notchy in some respects, but it's certainly consistent.
The box takes exactly 4 l so it's convenient to put the whole bottle in poured in from the top through the shifter housing with no wastage.

Previously I had a boutique 75w-90 synthetic(cougar) oil which was better all round, except for the occasional shift into 3rd which would baulk a bit.

Overall I think I would be inclined to stick with the VMX-M if it ever gets changed again, which probably won't happen due to the vehicle falling apart in other areas with over 400,000 kms on the clock.

 

[Shannow]

Originally Posted By: supercity

I also use VMX-M in my car where the spec is 80w GL-4. I find there are good and bad days. Some days its like silk, others the first shift into 2nd just doesn't want to go. Overall an improvement on the Penrite Pro Gear 75w85 synthetic.
As you probably know the original application was for Mitsubishi FF. Just curious, what would you refer to as a genuine GL-4?


Yep, was Penrite that I tipped out this time.

As to "proper" GL-4, here's something from a previous post.

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3952752/Re:_Just_what_is_the_GL-4_spec#Post3952752

There's been rumour that a "formulated" GL-4, rather than a half treat rate GL-5 is "better"...I dunno.

 

[zeng]

Originally Posted By: supercity
I also use VMX-M in my car where the spec is 80w GL-4. I find there are good and bad days. Some days its like silk, others the first shift into 2nd just doesn't want to go.Just curious, what would you refer to as a genuine GL-4?

One gets a good shift feeling in a manual transmission whenever the ratio of static COF to kinetic/dynamic COF is closer to 1 or thereabout.
At a ratio exceeding,say 1.8 and higher, one could be irritated by the 'rough' shift phenomenon.
However, in real life ...................
a smooth and consistent gear shiftability are elusive often times, as system parameters are continuously changing, whilst in intended operation, throughout the life of a particular lubricant and transmission hardware.

.....The bold in the wikipedia.org quotes below indicates some of those system parameters.......
Quote:
The coefficient of friction is an empirical measurement –it has to be measured experimentally, and cannot be found through calculations.[citation needed] Rougher surfaces tend to have higher effective values. Both static and kinetic coefficients of friction depend on the pair of surfaces in contact; for a given pair of surfaces, the coefficient of static friction is usually larger than that of kinetic friction; in some sets the two coefficients are equal, such as teflon-on-teflon.

Quote:
While it is often stated that the COF is a "material property," it is better categorized as a "system property." Unlike true material properties (such as conductivity, dielectric constant, yield strength), the COF for any two materials depends on system variables like temperature, velocity, atmosphere and also what are now popularly described as aging and deaging times; as well as on geometric properties of the interface between the materials.
.......... and operating viscosities.... possibly base oil stocks etc of lubricants in question.


Originally Posted By: Shannow
There's been rumour that a "formulated" GL-4, rather than a half treat rate GL-5 is "better"...I dunno.

"better" ...... in the context of smooth gear shiftability .Period.
Gear lubricants are more than shiftability.
In the now obsolete GL4 specification,synchronizer materials and material property in the likes of coefficients of friction (be it static, kinetic or its ratio) were NEVER part of the requirements in SAE GL4 specifications , neither were smooth shift property a requirement.

"formulated" GL-4 ???.....
"dedicated" GL-4 ??? ...... what?

There are non-manual trans oils like differential GL5 oils, CD/Sx engine oils,powershift transmission Cat TDTO/ Allison C4 oils, axle oils etc that, according to the relevant manufacturers/blenders, contains appropriate friction modifier additives for synchronizers to achieve desired static and kinetic coefficients of friction (and desired ratios),among other appropriate additive package, and claims to meet or exceed GL4 requirements.
JMHO.