Are all stock Dino GL-5 gear oils the same?

[S4Alfa]

Long time lurker here making his first post - and my question is limited only to modern conventional GL-5 rated gear oils, and whether they are all similar, that is, if a car manual asks for GL-5 conventional oil, would any conventional oil do?

I ask because I have an unusual car, a 1991 Alfa Romeo Spider. These cars have manual transmissions with notorious weak synchronizers, although mine are currently in good shape.

Alfa owners and manauls swear by GL-5 Shell Spirax 75w-90, because it does not have "friction modifiers" which cause synchro wear.

So my question is - since Spirax is very hard for me to find - (nevermind whether your corner store has it

), will any locally off the shelf GL-5 do the trick - even Supertech GL-5? And how do I know, in general if GL-5 oils have the friction modifiers? Is it all just #@$%!? Doesn't the fact that they are all rated GL-5 suggest that they are of nearly identical properties and additives?

I guess I'm just looking for something to replace Spirax, although it is a safe choice, Alfa owners are nearly superstitious that it is some super special oil, when I think it's just an old school GL-5 oil, and probably not much different from Supertech GL5 - and I just want to satisfy my curiousity here from anyone who is familiar with these two oils (Supertech). Keep in mind, I'm not looking for other high tech Redline or whatever - my question is really whether Spirax is necessary.

Thanks a lot for you insights and help - the easy way to find out would be to put some Supertech in, but like I said, I'm really just curious about this debate about Spirax being the ONLY oil to use in an Alfa.

And also, just curious what the conventional "GL-5" means - that is, if they are all different, then why put them in the same category?

 

[unDummy]

There are several Spirax products? which one? LS, S, HD?

Any GL5 gear oil that does NOT have LSD additive should work ok as long as change interval is reasonable. Most store branded GL5 gear oils that I've seen come with LSD additive. If the gear oil requires LSD additive, its a safe bet!

Since you require GL5, my recommendations are Redline 75w90NS, Motul Gear 300, Silkolene Silktran Syn-5, Neo 75w90HD, and RoyalPurple Maxgear. Sorry, but high tech is the way to go and provides the best performance and protection. Online stores will always have them. Napa/Pepboys seems to stock and can usually order the Royalpurple. Speed/4x4 shops will sometimes have the Gear300 and 75w90NS.

Its also funny that every specific vehicle forum has the 'best' fluid, which IMO is just a silly fad.

 

[S4Alfa]

unDummy - thanks very much for the response. Sorry, it is GL-5 Shell Spirax HD dino 75w-90.

Next inquiry is whether the SuperTech conventional 75w-90 product has LSD in it. Interval changes are 15-20k. Currently has Spirax in it, and it has performed fine. I mention Supertech, because I have a bunch of it - and I sort of want to prove to my Alfa buddies that even a "cheap" readily available oil will do fine in our Alfa application.

And yes, my purpose is as much to educate myself, as well as dispell the myth that there is only "one" or "best" fluid for my application. Spirax is a safe bet, only because its known not to have, what I guess is the LSD additive. Surely there are other high tech options, and I'll probably end up buying a product online.

But in the meantime, anyone know where I can find out if Supertech has the LSD friction modifier additive? Should it say on the bottle? Couldn't find it in a search here.

Thanks again!

 

[unDummy]

Read the bottle. If it doesn't mention it, use it. If you don't like the shift feel, then you'll end up dumping it anyway in 15k.
15k gear oil change intervals is excellent maintenance.

There is a VOA for Supertech 140wt. It looked pretty weak. But, it might be just right for manual transmissions.

 

[Bror Jace]

Additive packages vary widely amongst gear oils. There's the 'standard' add pack that reeks of sulphur. Chevron Delo and a few other conventional gea oils use a boron-based package. That's just two that are obviously different based on smell alone. Synthetics probably have even more differences.

As for which will work best in your transmission? Really hard to say as there are so many variables in play. Best is to try them for a few hundred miles each. Capacity should be relatively low so $$$ spent shouldn't be too bad.

 

[marco246]

S4Alfa,

I own a 71 Alfa, and I think there's very little difference between our cars' transmissions and differentials despite the 20 years. Like you, I've lately been puzzling over what gear oil to use. I bought a case of Shell Spirax 80W-90HD (GL-5) thinking it would do the trick for both applications, based on a recommendation in the International Auto Parts catalog. Then I read on the Alfa Bulletin Board that GL-5 was not recommended by some Alfa owners because it's too slippery for the synchros in the transmission and for the plates in the LSD.

I don't know one way or another. There are a lot of opinions out there, informed and otherwise, and I don't want to add to the noise. A member of this board, edhackett, gave me some advice which I've taken, and so far so good. An Alfa owner, too, he highly recommended Chevron Delo 80W-90 ESI for both transmission and diff. The stuff is rated GL-4 and GL-5. I bought a case from the local jobber, put it in the diff and transmission (but put the Spirax in the steering box) and promptly took the car to an SCCA Solo 2 autocross where it performed just fine.

So it works for me. You might consider it.

Cheers, Mark

 

[S4Alfa]

Thanks for the replies - and Mark, nice to know there are some other Alfa owners on here. Like many of you have mentioned, it looks like I have options and am not specifically limited to Spirax. The Supertech doesn't mention LSD or friction modifiers, and said it's safe for bronze and brass, which I understand Alfa hasn't used since the 60's. And Mark, you're correct, are transmissions are indentical, or nearly so.

So I'll give this cheap stuff a shot - just to satisfy my curiousity. The Spirax in there now has about 20K on it and is begining to feel a little tired, although it has been good to the synchros.

Thanks again for the responses. For what it's worth, the bottle of Supertech gear oil says WPP (Warren) on the bottom, and the motor oil says G, as in Mobil/Exxon. So I think they are good quality oils, good enough for my application anyway.

 

[y_p_w]

Quote:

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There are several Spirax products? which one? LS, S, HD?

Any GL5 gear oil that does NOT have LSD additive should work ok as long as change interval is reasonable. Most store branded GL5 gear oils that I've seen come with LSD additive. If the gear oil requires LSD additive, its a safe bet!

Since you require GL5, my recommendations are Redline 75w90NS, Motul Gear 300, Silkolene Silktran Syn-5, Neo 75w90HD, and RoyalPurple Maxgear. Sorry, but high tech is the way to go and provides the best performance and protection. Online stores will always have them. Napa/Pepboys seems to stock and can usually order the Royalpurple. Speed/4x4 shops will sometimes have the Gear300 and 75w90NS.

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I tried the Red Line 75W90NS from about 4K miles to 15K in my WRX. I didn't quite like how it shifted, so I then dumped it for Motul Gear 300. I'm pretty sure that Gear 300 is labeled as suitable for limited slip diff use.

 

[unDummy]

http://www.motorspot.com/Gear_300_Auto_3178_(GB).pdf

 

[y_p_w]

Quote:

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http://www.motorspot.com/Gear_300_Auto_3178_(GB).pdf

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That was dated 11/98. Maybe I can go home and check the bottle that I bought in 2005. I could have sworn my bottle said it was OK in limited slip diffs.

 

[unDummy]

Every GL5 gear oil is OK in LSDs. You'll just have to add the appropriate dose of LSD additive if using a cone or clutch type LSD. LSD additive isn't needed in most manuals, open diffs, and non-clutch LSDs.

For manual transmissions, finding a gear oil without any pre-dosed LSD additive is best.

Redline also seems to work best after a rinse run.

 

[y_p_w]

Quote:

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Every GL5 gear oil is OK in LSDs. You'll just have to add the appropriate dose of LSD additive if using a cone or clutch type LSD. LSD additive isn't needed in most manuals, open diffs, and non-clutch LSDs.

For manual transmissions, finding a gear oil without any pre-dosed LSD additive is best.

Redline also seems to work best after a rinse run.

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Well - I checked and didn't see anything on the bottle that said anything either way. Maybe there was no more room with 8 languages. I thought that by definition that GL5 is supposed to provide at least minimal LSD performance although I'd understand if they don't actually recommend it for that purpose.

Red Line 75W90NS does an end-around by saying that it meets the protection and performance characteristics of GL5 without actually saying it meets GL5. I've seen their LSD additive before.

 

[unDummy]

GL5 is an AW/EP rating for gear-type protection under loads. GL5 has nothing to do with LSD function.