Gear, Engine, and MTF Oils

[95metro]

I thought this info was generic enough that it could use its own thread. I've used the recommended manual transmission fluid for Swift Clones as a primary reference, but it still applies to general lubrication:

The transmission/gear oil discussion kind of peaked my curiosity so I've done a little research.

Apparently gear oils and engine oils are actually the same viscosities, but are given different measurements by the SAE to differentiate their uses:

SAE gear and engine numbers cover the same range of viscosities; for example, an SAE 30 engine oil has approximately the same viscosity as a SAE 85W gear oil. This is because the formulation of engine oils is very different to that of gear oils in the automotive industry. An engine oil is far more stressed than a gear oil because it must cope with combustion by-products and blow-by gases which severely degrade the oil. As a result engine oils contain a much wider variety of additives than gear oils. Although not ideal, an engine oil will function in a gearbox while a gear oil will destroy an engine.

Quoted from: http://www.wearcheck.com/literature/techdoc/WZA007.htm (stupid layout on the website, but good info)

A pdf on Redline's website confirmed this by helpfully stating the gear and engine viscosities. 75W90 gear oil is similar to 15W40 motor oil, but the GM/Penzoil Synchromesh is actually closer to 5W30 motor oil viscosity.

Here are some fluid comparisons:

Legend:
Pour Point: Pourability at temperature (°C)
Viscosity Index: The higher the number, the less change in viscosity throughout temperature range
cSt @ 40: Kinematic viscosity in centistokes at 40°C
cSt @ 100: Kinematic viscosity in centistokes at 100°C

Short bit on kinematic viscosity:

In order to determine the differences between the three oils one has to look at the kinematic viscosity of each lubricant. The kinematic viscosity is essentially the amount of time, in centistokes, that it takes for a specified volume of the lubricant to flow through a fixed diameter orifice at a given temperature.

Quoted from: http://www.synthetic-oil-tech.com/d....weight_oil.htm

Penzoil 75w90 GL-4 (basically what the Metro manual calls for, but it's not the correct stuff!)
http://www.pzlqs.com/Tech/Pdsheet/Do...E75W90GL-4.PDF
Pour Point: -42
Viscosity Index: 149
cSt @ 40: 108
cSt @ 100: 15.3

Penzoil Synchromesh (apparently this is the GM synchromesh)
http://www.pzlqs.com/Tech/Pdsheet/Do...omeshFluid.PDF
Pour Point: -50
Viscosity Index: 208
cSt @ 40: 41.6
cSt @ 100: 9.08

Amsoil Synchromesh 5W-30
http://www.amsoil.com/StoreFront/mtf.aspx
Pour Point: -45
Viscosity Index: 194
cSt @ 40: 47.1
cSt @ 100: 9.6

Royal Purple Synchromax
http://www.royalpurple.com/prodsa/scmax.html
Pour Point: -51 (their PDF states -40...???)
Viscosity Index: 196
cSt @ 40: 35.3
cSt @ 100: 7.7

Redline MTL (70W80 gear or 5W30 engine)
http://www.redlineoil.com/pdf/6.pdf (pdf for a number of Redline transmission fluids)
Pour Point: -50
Viscosity Index: 183
cSt @ 40: 56.2
cSt @ 100: 10.6

Mobil 1 5W-30 Synthetic (engine oil - just threw it in to see the difference)
http://www.mobil1.com/USA-English/Lu...bil1_5W-30.asp
Pour Point: -54
Viscosity Index: 169
cSt @ 40: 64.8
cSt @ 100: 11.3

EDIT: The characteristics of some of these MTFs is very close to some 0W30 motor oils. Looks like krousdb's method may be perfect...???

https://www.amsoil.com/storefront/tso.aspx

Mobil 1 0W-20 Synthetic (engine oil - spec sheet is discontinued - they appear to be changing the formulation)
http://www.mobil.com/USA-English/Lub...bil1_0W-20.asp
Pour Point: -57 (newer website info claims -53)
Viscosity Index: 165
cSt @ 40: 43
cSt @ 100: 8.4

[krousdb]

Yup, 0W-20 for me. Got any data on that?

[95metro]

What brand are you using?

[krousdb]

Mobil 1 of course.

[95metro]

Okay, added some Mobil 1 0W-20 info. It looks like they are changing the formula though. The data sheet was not available directly from the product description website.

So, Dan, what made you go with 0W-20 anyway? I just read a website where the guy claimed that 0W-20 isn't viscous enough for anything and he would be freaked out using it in an engine (though he didn't mention transmission I doubt he would even consider that either).

[krousdb]

If 0W-20 is the recommended viscosity for the HCH, it's good enough for my Prius, Del Sol and VX. The Prius is at 70K with 15K interval oil changes. Runs better than the day I got it and has never been serviced other than the routine maint that I do.

As far as 0W-20 in the tranny, if its good enough for an engine, why not a simple set of gears and bearings?

[GasSavers_katman]

I've been asking the techs at AMSOIL about this and they say that the engine oils don't have the shear strength of the gear lubes. It's all in the additive packages.

[GasSavers_Ryland]

gear oil has things like higher sulfer content that act as a high presure lube between the gears, sence they are presseing, and sliding, altho the sulfer wouldn't hold up well to the heat of the engine, it will also eat some forms of bronze, so unless your tranny calls for a gear oil, don't put a gear oil in! some trannys, like Honda's call for motor oil, or honda manual transmition oil, in a few minutes I have some Amsoil manual transmition fuild showing up that is suposed to be compatible with Honda's and work better then motor oil, we'll find out how it works.

[95metro]

Originally Posted by krousdb

If 0W-20 is the recommended viscosity for the HCH, it's good enough for my Prius, Del Sol and VX. The Prius is at 70K with 15K interval oil changes. Runs better than the day I got it and has never been serviced other than the routine maint that I do.

As far as 0W-20 in the tranny, if its good enough for an engine, why not a simple set of gears and bearings?

I'm amazed that it's actually the recommended fluid for hybrids - or at least the HCH! I didn't know that.

I also just looked at the data again and noticed that Royal Purple is apparently less viscous than 0W-20...???

So, now I am debating about giving 0W-20 a shot in the Metro for the upcoming winter. Obviously if I started hearing lifters clicking or synchros crunching then I wouldn't continue use.

As an alternative I'm very certain that 0W-30 would work perfectly since it's still 30 weight oil. I'm mostly concerned about the -20?C/-4?F weather when things get gummy.

[krousdb]

Yup, I was looking at Bob Barlow's HCH during the Prius Matathon weekend and noticed on the oil filler cap (I think that is where I saw it) 0W-20 Oil. They come from the factory with a special break in oil.