high dollar oil question

[aa8jzdial]

A good old buddy who is a whiz bang shade tree sube guy but a worthless Internet fellow wants to know about using some designer style gear lube for his manual transmissions and maybe also there motor oil.

 

Any insight into stuff called Amsoil?

 

Is it worth the big bucks?

I am skeptical but told him I would seek data from the world's Sube guys.

thanks

rick

[ScoobySchmitty]

I use an Amsoil product in my vintage 2-stroke mopeds called Amsoil Saber. It's advertised as being able to run as lean as 100:1. Most 2-stroke moped engines require a mix of 50:1. I've run Saber at 100:1 mix in one of my bikes before, through a whole tank, about 70 miles. Not a single problem. I did notice a slight decrease in performance, but running that lean on oil usually means a seize within a few miles. Bottom line, I trust Amsoil's product line to be all it says it is.

[Scoobywagon]

I've used Amsoil extensively in the past. EXCELLENT product. In a reasonably clean engine, it is not unreasonable to change the oil every 30k with filter changes and top-offs every 3k. The gear oil is also very good stuff. It is quite possible that this may be the last oil change those diffs ever get. Stuff lasts a long time, keeps temps down. Its spendy, but an extraordinarily high quality product.

[GeneralDisorder]

Depends on the tranny in question. If it's half shot already then no amount of designer lube will help it. Best thing is to open it up and change the naughty bits out.

 

If it's brand new..... maybe but why? Subaru manual transaxles tend to last a good long time anyway and frankly are simple to rebuild. Most never have the gear oil changed once and last 200k+ without incident even.

 

If it were me - I would use a quality name brand gear lube (not Amsoil) and change it every 30k. You are going to get more benefit from changing the oil and running a few hundered miles with ATF to flush it between changes than you would ever get from dumping in Amsoil and leaving it for the life of the trans.

 

There is no substitute for regular maintenance, and anyone representing a bottle of fluid that purports to be the last oil you will ever buy is selling you a bill of goods.

 

I beleive in synthetics - for the right application. A Subaru passenger car transaxle isn't the right application. Unless you are towing or severely abusing the thing in some other way that will apply great amounts of heat or shearing forces to the lube you don't need them. The fact of the matter is that 95% of these transmissions will outlast the engine by a good stretch.

 

GD

[idosubaru]

Amsoil is a great product and high quality. It's not a magic elixir.

 

And I also agree with GD.

[RallyKeith]

NEVER run straight synthetic gear oil in a subaru transmission, regaurdless of the brand. Transmissions and specifically syncros work on friction. ANY synthetic straight out of the bottle has a different coefficient of friction than it's regular (Dino Oil) equvilant. There are TONS of discussion on the topic on places like NASIOC because of issues in higher perfomance and tuned cars. Here is a very detailed thread discussing some of this.

http://forums.nasioc.com/forums/showthread.php?t=986710

 

We run only regular gear oil in our Rally car because we very quickly destroyed a gear box using synthetic. Like GD said, subaru transmission last so long anyway when properly maintained that it's just not worth it.

 

Keith

[bulwnkl]

The trick is to know the difference between gear oil and (synchronized) manual transmission lube. That's where the different frictional properties lie. 'Synthetic' manual tranny lubes are better for the tranny and synchros than 'conventional' gear lube. Specialty Formulations (now defunct) used to have a superb mtl for Subies. If you're comfortable with a GL4 gear lube in a Subie rather than a GL5 (personally, I'm not), then Amsoil has an mtl for you (can't recall the name), or you could use Red Line's MT-90. Red Line's 75W90NS isn't actually a synchronized manual transmission lube, but they do leave out the particular friction modification package that most people describe as 'too slick' in terms of how they describe synthetic gear lubes.

 

The fact is, though, that Subaru transmission just shift poorly. Fluid changes can only help that a certain amount.

Edited January 13, 2010 by bulwnkl

[frag]

NEVER run straight synthetic gear oil in a subaru transmission, regaurdless of the brand. Transmissions and specifically syncros work on friction. ANY synthetic straight out of the bottle has a different coefficient of friction than it's regular (Dino Oil) equvilant.

 

Keith

 

 

Question: I can readily understand that gear oil that is too "slipery" will make changing gears a little harder cause of less friction on the synchros (is that what you're saying?) but how would that lead to trany destruction on a road car?

Just want to know.

G.

[GeneralDisorder]

If they syncro's fail to work then you grind the shift dogs on the gears to pulp and all that metal goes into the bearings......

 

GD

[RallyKeith]

If they syncro's fail to work then you grind the shift dogs on the gears to pulp and all that metal goes into the bearings......

 

GD

 

 

Exactly!

 

Also, if you read the first post of that NASIOC thread I listed it goes into detail about the issue of the subaru gearbox being a single unit with the diffs and the output gears and the syncros sharing the same fluid. Each type of gear and mechanism responds differently to changes in the fluid, and with the subaru design, changes that help one thing hurt another.

[GeneralDisorder]

Yep - if only we didn't have a differential inside the tranny! The hypoid gear ruins it for us. Otherwise we could all just run ATF And be happy as a clam like every other RWD race car out there.

 

GD

[frag]

If they syncro's fail to work then you grind the shift dogs on the gears to pulp and all that metal goes into the bearings......

 

GD

 

Does that mean that if I dont feel or hear any grinding, I'm ok ?

[GeneralDisorder]

You are probably fine in the short term, yes. If you don't have any grinding then you likely aren't shifting hard/fast enough to have a problem with the sythetic you are using. There's nothing about the synthetics that are going to damage the transmission other than their tendancy to cause more grinding.

 

They are expensive and uneccesary and often provide worse performance than the non-sythetics is our point. You'll get much better performance and transmission life from using regular quality gear oil along with a flush/change maintenance schedule.

 

GD

[frag]

You are probably fine in the short term, yes. If you don't have any grinding then you likely aren't shifting hard/fast enough to have a problem with the sythetic you are using. There's nothing about the synthetics that are going to damage the transmission other than their tendancy to cause more grinding.

 

They are expensive and uneccesary and often provide worse performance than the non-sythetics is our point. You'll get much better performance and transmission life from using regular quality gear oil along with a flush/change maintenance schedule.

 

GD

 

Thanks for the info.

G.

[bulwnkl]

it goes into detail about the issue of the subaru gearbox being a single unit with the diffs and the output gears and the syncros sharing the same fluid. Each type of gear and mechanism responds differently to changes in the fluid, and with the subaru design, changes that help one thing hurt another.

Guys, this makes absolutely no sense as a Subaru-specific issue. All (essentially) transaxles are designed and built this way; the transmission and final drive are all in the same case sharing the same fluid. The only thing 'unique' about the Subaru is that the final drive (aka differential) is a hypoid unit, whereas transverse-mounted front-drive transaxles (aka nearly all front-drive transaxles now) generally do not employ hypoid final drives/diffs. There's still "the diffs and the output gears and the syncros sharing the same fluid."

 

The presence of the hypoid unit (which is essentially just a matter of where & at what angle the pinion is located relative to the ring gear) is why Subaru specifies a GL-5 gear oil rather than a GL-4 or GL-4/5 like most transaxles. To be clear, though, nearly everyone who ever changes the gearbox oil on any transaxle ends up putting a GL-5 fluid in. That the Subie doesn't shift all that well is more a design issue than anything else, but I certainly agree that all synchronized transaxle fluids can significantly impact both durability and shift quality.

Edited January 15, 2010 by bulwnkl

[GeneralDisorder]

Specially forumlated MT fluids and/or ATF (which is now very common in the newer MT's being built) can take advantage of the transmission not having the hypoid diff - it requires a formulation that protects against the heavy loading of the hypoid gear teeth. More sulferizing compounds from what I've read.

 

Anyway - the Hypoid puts a requirement on the gear oil that doesn't jive with the fluids that make for pretty shifting. There is nothing out of the ordinary with the Subaru syncro design. It's about the same thing that you will find in any other transmission.

 

GD

[bulwnkl]

Anyway - the Hypoid puts a requirement on the gear oil that doesn't jive with the fluids that make for pretty shifting.

That's simply not true. The two things are entirely different.

 

I agree that the difference between a GL-4 and a GL-5 fluid is almost universally the treat rate of the Extreme Pressure (EP) add pack. It is done this way for manufacturing/production simplicity. In most gear oils, the EP add is still primarily a deactivated Sulfur-Phosphorus package, though some companies use Borates instead.

 

Nevertheless, the dynamic friction modification needed for good synchronizer performance is not precluded in any way by the EP add treat rate needed for hypoid protection. The reason you see nearly all synchronized manual transmission fluids rated as a GL-4 is simply because nearly all manual transmissions need only GL-4 levels of protection. The reason you see more and more transmissions using lighter, ATF-viscosity fluids (and even ATF in many cases) is primarily for fuel efficiency and to be able to get the gear lube to flow well throughout the case to all parts which need it.

 

The nice thing about Specialty Formulations was that, if you simply asked them to, they'd increase the EP treat rate in any of their manual transmission lubes to GL-5 levels. Then you had the proper dynamic friction modification for the synchros, but a GL-5 level of protection. Worked beautifully in my XT-6.

 

**EDIT**

I forgot to add that Red Line's 75W90NS product is often used in Subaru transmissions, but it isn't a manual tranny lube. While it lacks the friction modifiers that make many gear oils 'too slick' for synchronizers, it does not, to the best of my knowledge, contain the friction modifiers for outstanding synchro performance. I believe this is part of the reason that many Subie owners find it less than perfect as a manual tranny fluid in our cars.

Edited January 15, 2010 by bulwnkl

[GeneralDisorder]

Interesting - I heard that Subaru was supposed to be putting out a gear oil forumation for their race cars to the dealers to sell. I don't know of that ever came to pass - I think it was said that it was only availible in 5 gallon units at a pretty unreasonable price for the average user. They were apparently considering selling it in quarts if there was enough demand.....

 

Never did hear what came of that but then I haven't been looking for it either.

 

So it's just a matter of no one makes a "perfect" gear lube for our transmissions - at least not for the performance minded folks that want to shift them like they are going around a track every day.....

 

GD

[bulwnkl]

Yeah, any gear oil will do just fine, as long as you don't want to shift the car today.

 

Interestingly, the head physicist/chemist/tribologist/formulator at the former Specialty Formulations didn't seem convinced that Subarus needed a GL-5 level of EP additives. I know that, in a super-generic way, the GL-4 rating is 'for' heavily loaded hypoid gears, though GL-5 obviously can help protect things that are more heavily loaded. Maybe he had actually done some load calculations on a Subie diff? I didn't get that far into it with him, since I was able to get a GL-5 treat rate from them easily.