Lucas 85W-140 formulation change - anyone have specific info?

[pentode]

I ordered some Lucas 85W-140 from rockauto for my old Datsun that has brass synchros. The picture they have on their website claims to be a GL-4 and GL-5 compatible oil. However, what I received is labeled GL-5 only. I called Lucas and got the most confusing answer possible. They said "We've changed the formulation and the label. It used to say GL-4 but it was not yellow metal safe, now it only says GL-5 but I've talked to our technicians and they say it's yellow metal safe. However, we can't recommend you try it."

Does anyone out there have good, specific info about what's going on here? Do I need to return this stuff? I'm very hesitant to use it on a 40-year old transmission if there's any chance it's unsafe.

 

[Bailes1992]

There's loads of MTF's here in Europe that carry both GL-4 and GL-5. It's actually quite handy as you can safely use them in manual transmissions and diffs.

However, I wouldn't trust that bottle. Especially after the utterly ridiculous response from Lucas themselves.

 

[JavierH19]

If you need gl4 for a manual trans then that won't do it. It may be a slightly different one that looks mostly similar. You should return it or keep it for the differential which doesn't need gl4.

 

[MolaKule]

What was the original Owners Manual requirement? Most older MT's used either a 75W90 or 75W80 to 85.

 

[pentode]

What was the original Owners Manual requirement? Most older MT's used either a 75W90 or 75W80 to 85.

It wanted GL-4 between 75 and 140 weight, depending on ambient temps. This is one issue - the car is only driven in summer and the temps are getting so hot that I'm afraid the 75W-90 I have in it might be on the thin side. There's a story, but the short version is that I rebuilt the trans a couple years ago and at the time, no synchros were available. The old ones measured in spec, so I reused them but now, 2nd is a tiny bit balky when it's cold. I know it might be counter-intuitive but I've been wanting to see if a thicker oil would give a bit more grip on the synchros when the cold tolerances are fractionally loose.

The thing is, the car is only driven when it's hot outside and 75W is pretty much for cold weather driving. However, the only GL-4 I was able to get locally was 75W90

 

[ceecbtg]

They don't know what to say because it's a marketing lie. It's safe, but not safe, but say GL4 +GL5, but now GL5 only.
If you car needs GL4 only, then you are doing bad even if bottle says GL4 + GL5.
85w140? uhh

 

[MolaKule]

It wanted GL-4 between 75 and 140 weight, depending on ambient temps. This is one issue - the car is only driven in summer and the temps are getting so hot that I'm afraid the 75W-90 I have in it might be on the thin side. There's a story, but the short version is that I rebuilt the trans a couple years ago and at the time, no synchros were available. The old ones measured in spec, so I reused them but now, 2nd is a tiny bit balky when it's cold. I know it might be counter-intuitive but I've been wanting to see if a thicker oil would give a bit more grip on the synchros when the cold tolerances are fractionally loose.

View attachment 232977

Interesting chart.

Oil viscosity has little to do with synchro "grip." It's the friction modifier chemistry that determines engagement/disengagement characteristics.

Modern application specific MTF's with the GL-4/GL-5 ratings are safe for copper-alloy components.

Here's some extra info on MTF's:

https://bobistheoilguy.com/forums/threads/updated-list-of-mtfs.383388/

 

[pentode]

They don't know what to say because it's a marketing lie. It's safe, but not safe, but say GL4 +GL5, but now GL5 only.
If you car needs GL4 only, then you are doing bad even if bottle says GL4 + GL5.
85w140? uhh

According to the factory service manual, 140W should be fine, and in fact required in some of the conditions I drive in. I know it may sound heavy to someone used to more modern transmissions, but that's what Datsun wanted back then. There are oils that are safe for both GL-4 and GL-5, but none of them are available where I am.

Interesting chart.

Oil viscosity has little to do with synchro "grip." It's the friction modifier chemistry that determines engagement/disengagement characteristics.

Modern application specific MTF's with the GL-4/GL-5 ratings are safe for copper-alloy components.

Here's some extra info on MTF's:

https://bobistheoilguy.com/forums/threads/updated-list-of-mtfs.383388/

So in this case, given that they've taken off the GL-4, probably follow my initial thought and just avoid using it?

EDIT: Oh, and thanks for the link to that list of MTFs- in fact I've referred to that before while shopping for gear oil. The problem is that virtually nothing on that list is available in Canada as far as I can tell. At least nowhere near me nor any mail order I can find.

EDIT2: Misspoke - none of the GL-4 oils on that list are available here, I'm sure others are.

 

[pentode]

This is for the trans, not the rear end. And GL-4 oils are nigh on impossible to find in these parts. Took me several months to get some here and that was only because the local Carquest ordered some by accident.

If I lived in the USA this would all be moot. Or Europe. I was able to buy GL-4 at the supermarket over there.

 

[Oillover]

However, I wouldn't trust that bottle. Especially after the utterly ridiculous response from Lucas themselves.

+1
It would be foolish to take the chance, especially when the manufacturer won't even stand behind their own product.