Gear oils that claim GL-4 / GL-5

[FCD]

Many gear oils on the market seem to claim to meet both GL-4 and GL-5 as the same time, isn't this impossible though?
As GL-4 has too little phosphorous to protect Differentials
And GL-5 has too much so it eats away at syncros and makes them slip.

What is it, an intermediate?

Also, what is up with GL-4+?

 

[Mainia]

https://www.redlineoil.com/75w90-ns-gl-5-gear-oil

 

[aquariuscsm]

Afaik GL4 is synchronized transmission specific. A GL5 fluid will cause gear crunch when you shift (unless the transmission is dual spec for both).

 

[Job]

You have to trust the oil supplier. If Chevron for example says GL4, GL5, and MT1 on the bottle you have nothing to worry about as to metals or anything else.

 

[Bill_W]

I did a similar post here...
https://www.bobistheoilguy.com/foru...-gl-5-gear-oils-a-compromise#Post5385030

 

[tc1446]

And then the Aisen? manual transmission on my Slingshot with an Ecotec 2.4 calls for GL-3. Try to find one, other than the Polaris brand.

 

[Rand]

most of the gl-5 rated wont shift as well as a gl-4 gear oil in a transmission.

the specific application of gl-5 gear oil in a manual transmission is usually some sort of shared sump arrangement with a differential that requires gl-5.

such as most MT equipped subarus.

A gl-3 rated gear oil might be able to use motor oil.

 

[Gebo]

Originally Posted by tc1446
And then the Aisen? manual transmission on my Slingshot with an Ecotec 2.4 calls for GL-3. Try to find one, other than the Polaris brand.



PM Molakule.

 

[Bailes1992]

I too always thought GL-4 was for manual synchronised transmissions and GL-5 for differentials etc but have found out recently that it is simply not the case. The API GL-* ratings are much like API S* or C* where one supersedes the other.

API GL-4 is technically now obsolete. I suspect it's still around due to the age-old stories of GL-5 oils damaging older brass components which is no longer true. I suspect this is where/why manufacturers are putting GL-4/GL-5 on bottles.

A manual transmission oil is a manual transmission oil regardless of the API rating. I use Fuchs Sintopoid 75w80 in most manual gearboxes and that meets API GL-5.

 

[pbm]

Torco makes a low viscosity MTL that's GL-5 but claims to be 'yellow metal safe'.
I had considered it for my 14' Focus's MTX-75 which requires 75W GL-4 (hard to find).
The Torco rep. said it would work great so I bought it but still haven't used it. I ended up getting
Volvo's MTL which meets the Ford spec. but is cheaper (Volvo used the MTX-75 in some models
when they were partnered with Ford)....It works well....I may use the Torco at some point or try to
sell it on here....or CL..

 

[AC1DD]

Originally Posted by Bailes1992


API GL-4 is technically now obsolete. I suspect it's still around due to the age-old stories of GL-5 oils damaging older brass components which is no longer true. I suspect this is where/why manufacturers are putting GL-4/GL-5 on bottles.

.


False. Many people believe this due to the change in number upward, the truth is that GL-4 is not obsolete and this isn't because of metal damage but the additives
and amount in GL-4 that lend to very good sychronizer performance and smooth shifting as well in light duty passenger vehicles.

If your vehicle specifies GL-4 spec product USE just that. Do NOT use GL-4/5, GL-4+, ect it will likely give you poorer shifting characteristics.

 

[AC1DD]

Originally Posted by pbm
Torco makes a low viscosity MTL that's GL-5 but claims to be 'yellow metal safe'.
I had considered it for my 14' Focus's MTX-75 which requires 75W GL-4 (hard to find).
The Torco rep. said it would work great so I bought it but still haven't used it. ..


Don't believe everything a salesman says.

 

[RDY4WAR]

Originally Posted by pbm
Torco makes a low viscosity MTL that's GL-5 but claims to be 'yellow metal safe'.
I had considered it for my 14' Focus's MTX-75 which requires 75W GL-4 (hard to find).
The Torco rep. said it would work great so I bought it but still haven't used it. I ended up getting
Volvo's MTL which meets the Ford spec. but is cheaper (Volvo used the MTX-75 in some models
when they were partnered with Ford)....It works well....I may use the Torco at some point or try to
sell it on here....or CL..


I used a GL-5 75w-90 in my MTX-75 and had flawless operation for over 100k miles. That included a lot of racing use.

 

[AC1DD]

Originally Posted by RDY4WAR


I used a GL-5 75w-90 in my MTX-75 and had flawless operation for over 100k miles. That included a lot of racing use.


Which product was it and what did the label say exactly? GL-5 MT-1? or ?

The point is why use GL-5 when the manufacturer Ford specs a GL-4 fluid?
Lucky for you it worked out but it might not for others. Why chance it when there are tons of good GL-4 products out there that are inexpensive and shipped free to your door?

 

[RDY4WAR]

Originally Posted by AC1DD
Originally Posted by RDY4WAR


I used a GL-5 75w-90 in my MTX-75 and had flawless operation for over 100k miles. That included a lot of racing use.


Which product was it and what did the label say exactly? GL-5 MT-1? or ?

The point is why use GL-5 when the manufacturer Ford specs a GL-4 fluid?
Lucky for you it worked out but it might not for others. Why chance it when there are tons of good GL-4 products out there that are inexpensive and shipped free to your door?


It was Mobil 1 Syn Gear 75w-90. I made the switch by recommendation of a renowned MTX-75 builder (who passed away in 2016, RIP) because we kept burning up synchros. After going to the GL-5 oil, that transmission shifted flawlessly for several years of racing and a lot of street miles.

Note that I'm by no means trying to state that a GL-5 is ideal, but it happened to work in that application. The only downside was it was a little stubborn to shift if it was a really cold morning, but that went away after a couple times through the gears.

 

[AC1DD]

Originally Posted by RDY4WAR

It was Mobil 1 Syn Gear 75w-90. I made the switch by recommendation of a renowned MTX-75 builder (who passed away in 2016, RIP) because we kept burning up synchros. After going to the GL-5 oil, that transmission shifted flawlessly for several years of racing and a lot of street miles.


But here's what Mobil actually says about that product

Quote
After reading all the back and forth I decided to go to the source so I sent an e-mail to Mobil and received the following reply.

Thank you for your inquiry,

Mobil1 75W90 gear oil is an API GL-5 rated and should not be used in manual transmissions that require an API GL-4.


--
Thank you for choosing ExxonMobil products.
If you need further assistance, please contact ExxonMobil at 1-800-ASK-MOBIL

-Matt Jacob]


Another rep for Mobil said this

Quote

"Mobil1 75W90 gear oil is rated API GL-5 and it can harm the yellow parts that are utilized in most manual transmissions. Most manual transmissions require an API GL-4 rated lubricant ."

 

[RDY4WAR]

Originally Posted by AC1DD
Originally Posted by RDY4WAR

It was Mobil 1 Syn Gear 75w-90. I made the switch by recommendation of a renowned MTX-75 builder (who passed away in 2016, RIP) because we kept burning up synchros. After going to the GL-5 oil, that transmission shifted flawlessly for several years of racing and a lot of street miles.


But here's what Mobil actually says about that product

Quote
After reading all the back and forth I decided to go to the source so I sent an e-mail to Mobil and received the following reply.

Thank you for your inquiry,

Mobil1 75W90 gear oil is an API GL-5 rated and should not be used in manual transmissions that require an API GL-4.


--
Thank you for choosing ExxonMobil products.
If you need further assistance, please contact ExxonMobil at 1-800-ASK-MOBIL

-Matt Jacob]


Another rep for Mobil said this

Quote

"Mobil1 75W90 gear oil is rated API GL-5 and it can harm the yellow parts that are utilized in most manual transmissions. Most manual transmissions require an API GL-4 rated lubricant ."


I'm very aware. Just sharing my experience. I never got a used oil analysis on that gear oil, but like I said, it shifted great. Like I also said, I'm not recommending doing what I did. It could very well be something different that he did when he built it that made it work well.

 

[Cdn17Sport6MT]

Originally Posted by AC1DD
Originally Posted by Bailes1992


API GL-4 is technically now obsolete. I suspect it's still around due to the age-old stories of GL-5 oils damaging older brass components which is no longer true. I suspect this is where/why manufacturers are putting GL-4/GL-5 on bottles.

.


False. Many people believe this due to the change in number upward, the truth is that GL-4 is not obsolete and this isn't because of metal damage but the additives
and amount in GL-4 that lend to very good sychronizer performance and smooth shifting as well in light duty passenger vehicles.

If your vehicle specifies GL-4 spec product USE just that. Do NOT use GL-4/5, GL-4+, ect it will likely give you poorer shifting characteristics.


^^++1