alternatives to GL1 gear oil

[grasshopper]

Hi all. I went to local Napa store to ask if they had GL 1 oil. They sold me some Castrol HD 30 and said it will be the same. Is this stuff safe to use for 124 tranny or should I return it ?

[18Fiatsandcounting]

Oh boy, you've opened up a can of worms here, and opinions vary widely on this question. Here's what I can tell you:

1) The SAE (Society of Automotive Engineers) viscosity scale is different for motor oils than for gear oils, and a 30 weight motor oil is actually roughly the same viscosity as a 80 or 85 weight gear oil.
2) With that being said, transmissions have entirely different oil needs than engines, and so I would be hesitant to run an HD (High Detergent) motor oil in a Fiat transmission.
3) The GL-1 through GL-6 rating scale is an API (American Petroleum Institute) creation for gear oil. GL-1, 2, 3, and 6 are not in use anymore, not because there aren't older transmissions that use them, but because the cars that do use them are getting scarcer and scarcer and so it's not economical to produce, test, certify, and stock these oils. As such, GL-4 and GL-5 are the only oils commonly available.
4) The Fiat transmission specifies GL-1.
5) GL-4 and GL-5 are EP (extreme pressure) oils developed for use in high stress meshing gear environments (modern transmissions). To make them EP, there are sulfur additives, but the problem here is those sulfur additives cause more rapid wear on transmissions with older brass synchronizers (like the Fiat).
6) Can you use GL-4 or GL-5? GL-4 contains less sulfur additives, so you could probably use it in a Fiat transmission but it's not ideal over the long term. I would not use GL-5 as it has more sulfur additives and definitely would cause trouble with your synchros over time.

The good news in all of this? GL-1 is still available, and so if you really want to treat your Fiat transmission kindly, I would just order some. It's not like you have to change it very often.

I would return the Castrol HD-30 oil to the parts store, and in fact, I have heard that NAPA parts stores can order GL-1 for you. Whether they want to do that depends on how friendly and helpful your particular store is.

-Bryan

[kilrwail]

You can also use Pennzoil Synchromesh which is designed for engines with yellow metal synchronizers.

[aj81spider]

I got GL-1 from my local auto parts store (I'm pretty sure it was NAPA).

I would use that, as it's what Fiat specified. There's a lot of discussion around transmission oils, but why risk it if you can get the specified oil?

[SteinOnkel]

Here's a GL-1:

https://www.tractorsupply.com/tsc/produ ... luid-2-gal

[MattVAS]

Here is another link because it turns out we carry it too!
https://www.vickauto.com/newstore/index ... dk3gr3vbu3

[grasshopper]

I got a refund at Napa. Napa Canada does not carry GL 1 gear oil though. I can't seem to find any. I don't want to import it from the U.S.A as it costs a fortune in currency exchange, then shipping and duties. Does anyone have any leads in Canada or a safe alternative ? Thanks.

[kilrwail]

I'm in Canada. That's why I use Pennzoil Synchromesh.

[Jon124]

There are a few options available at Canadian tire.

I am currently using royal purple max gear. It advertises as safe for yellow metal. I have been using it for about 2 years and it shifts really nice. Only downside is it’s very expensive.

Mystic JT-7 also shows on the data sheet that it is safe for copper alloys. I think I will try this next time since it’s quite a bit cheaper.

I have also tried redline MTL and it was terrible. The transmission always ground gears when shifting and when I changed the oil it came out with a lot of flake. I think the problem was it is too light of viscosity.

[SteinOnkel]

Why don't you guys e-mail Matt and ask if he'll ship to Canada?

I have to order stuff from mainland Europe all the time, so don't gimme no bellyaching about customs and shipping.

[Jimb]

It makes a big difference in cost if the supplier is willing to ship via USPS and note on the package it VINTAGE AUTO PARTS (which are duty free in Canada).
UPS and FedEx always bill duty and a ridiculous service charge for paperwork, over and above the quoted shipping charges.

Jim