Don't use GL-5 oil in MR2 gearboxes

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Don't use GL-5 oil in MR2 gearboxes

Post by shinny » 15/05/18 17:02

Just popping a sticky into the forum for something I've found out in the last few months...

Although the Toyota manual says you can use GL-3, GL-4 or GL-5 oil in your gearbox, but this isn't true. As far as I understand it, the additives in GL-5 oil will bind too strongly to brass syncho rings, causing premature wear and slowly degrading shift quality. I don't believe there is a fix other than the expensive process of cracking open the box and switching out the parts.

Therefore do not put GL-5 oil in any SW20 gearbox!

How did I discover this? I put Comma LS80W90 (a GL-5 oil) into my turbo's E153 gearbox to smooth out a very aggressive plate LSD. I started to experience deterioration of the shift over a course of 6-7 years to something that was getting rather clunky by the time I laid her up awaiting reshelling. I've now edited everywhere I reference that oil on the forum. Please learn from my mistake.



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Re: Don't use GL-5 oil in MR2 gearboxes

Post by Gazza_DJ » 15/05/18 17:36

This has been known for some time, Bill Strong has a good write up on it with photos showing the damage it can do: http://racingstrong.com/?p=218
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by TonyleFrog » 15/05/18 19:26

I thought it was received wisdom that MT90 is the 'right stuff'.
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by Gazza_DJ » 15/05/18 19:52

MT90 is the popular option, but any good quality GL4 will do well.
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by MR2DI4 » 15/05/18 22:04

Have been running Castrol Syntrax 75W-90 in mine for the last 18 years+ and the gearbox is still like new in terms of its shifting.

Its GL-4 and GL-5 so no problems with it at all.

If you have gearbox oil problems then it is OIL SPECIFIC and not GL-5 SPECIFIC.

If the oil degraded your gearbox then the oil was crap.

It is unfortunate to find out the hard way, but time is the only true test for oil and that goes for your engine oil as well. After 20 years with the same car, I know what works.

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Re: Don't use GL-5 oil in MR2 gearboxes

Post by shinny » 15/05/18 22:25

Gazza_DJ wrote:
15/05/18 17:36
This has been known for some time, Bill Strong has a good write up on it with photos showing the damage it can do: http://racingstrong.com/?p=218
Yup, I read that; couldn't remember how to get back to it. Would have loved to have known that back in 2010, but that article was written in 2015. I don't think I'd ever seen the info posted on here though, hence I thought I'd make a sticky.
TonyleFrog wrote:
15/05/18 19:26
I thought it was received wisdom that MT90 is the 'right stuff'.
Not always.

MT90 doesn't work well once you get to plate diffs - I started with a gearbox full of it and, even with a friction modifier, it was seriously detracting from the car's driveability.

Otherwise it is the internet's choice, just like A'PEXi are the best air filter because someone said so once on a supra forum, but it's expensive compared to other GL-4 oils that will work just fine too.
MR2DI4 wrote:
15/05/18 22:04
If you have gearbox oil problems then it is OIL SPECIFIC and not GL-5 SPECIFIC.
If you know a specific GL-5 that doesn't have synchro eating additives then that's great for you. But even if only 50% of GL-5s will eat your synchros, if 100% of GL-4s won't then the goto advice of avoiding GL-5 is still a very wise starting point.

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Re: Don't use GL-5 oil in MR2 gearboxes

Post by peteV6R5 » 15/05/18 23:05

now you said, had a look round, loads of info on web re this from manufactures and retailers.
didnt actually know what was in mine apart from redline, thats what made me look. :D
want aware of the difference to be honest. well worth putting it out there Mark.
https://www.redlineoil.com/mtl-75w80-gl-4-gear-oil
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by MR2DI4 » 15/05/18 23:30

Yeah its pretty sad the number of Myths floating about the internet about the MR2 in general. Some idiot posts something and then everyone believes it. Its sometimes a great resource, like YouTube clips on "How to do something", it can save you time and money but in other areas its better to go with your own common sense gained over time.

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Re: Don't use GL-5 oil in MR2 gearboxes

Post by Gazza_DJ » 16/05/18 10:14

MR2DI4 wrote:
15/05/18 22:04
Its GL-4 and GL-5 so no problems with it at all.

If you have gearbox oil problems then it is OIL SPECIFIC and not GL-5 SPECIFIC.

If the oil degraded your gearbox then the oil was crap.
Absolutely not true. The problem is it's a slow death, it could take tens of thousands of miles for the effects to make themselves known. If an oil meets the GL-5 spec, it *will* damage the brass synchro's in an MR2 transmission to some extent. Read the link posted above to Bill's website.

Keep using the wrong oil if you think it works for you, I don't care. Please don't recommend other people on the forum fill theirs up with the wrong stuff.
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by MR2DI4 » 16/05/18 11:12

You did read the part where I said I have been using it for 18+ years right ?

Considering most people never change the oil until the gearbox "censored" itself anyway and have probably gone through 3 gearboxes already and mine is on track to last the lifetime of the car, I would say the Castrol Syntrax should be at the top of list for the "Right Stuff" to use.

Then again I don't listen to other people so why would I expect anyone else to take my advice. Not sure why I bother posting anything on here to be honest, will probably pack it in when I get the Suzuki GSXR750.

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Re: Don't use GL-5 oil in MR2 gearboxes

Post by Gazza_DJ » 16/05/18 11:37

I did, and that's great for you. I'll take the advice from people who work with these transmissions and have seen the damage GL-5's do to the synchro's in our transmissions time and time again.

The API classification only rates protection for the gears, not the synchros, so the API classification is only half the story. An oil can meet both the GL-4 and GL-5 specification for gear protection, but an oil that meets the GL-5 specification *will* damage the brass synchro's that our transmissions use. It's just a matter of time (mileage/shifts).
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by MR2DI4 » 16/05/18 23:00

So the damage MUST be evident by the condition of the oil when you drain it.

Logic would suggest the oil is discolored ? probably with a shade of black ?

By the way Brass never gets used in a gearbox, it may look like brass but its materials like phosphor bronze that get used for bearing materials.Toyota would not use brass, not even in 1989.

In addition, after 60,000km the Castrol Syntrax comes out the same colour as it went in. The only trace evidence in it is some tiny silver particals in suspension which I can assume are wear partials from gears. You can only see them in strong sunlight as they reflect the light.

Last change I put a neodymium magnet in the gearbox drain plug so when that comes out it will be very interesting to see whats on this and whats still in the oil. All bearing materials are non ferrous so they will not be on the plug but still in the oil. I'm expecting a small buildup of silver metal from the gears themselves on the plug, this would be normal wear, the less partical buildup the better the oil.

Its a free world, use whatever oil you want, put baby oil in your gearbox and a dab of Vaseline on the drain plug I don't care. The decent oils expensive. Use a GL-4 and change it every 50,000km and the gearbox will last a lifetime.

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Re: Don't use GL-5 oil in MR2 gearboxes

Post by MR2DI4 » 16/05/18 23:57

Hang on a minute lets consider a more likely scenario than the oil companies being at fault.

What is more likely is the transmission companies are NOT using OEM synchro's when they rebuild the gearbox.

I would put it out there that Mr Wong from Shenzhen in China is banging them out in his back yard shed for 1/4 of the price as the ones from Toyota in Japan.

Yes they do the job for a while but Mr Wong didn't do a course in metallurgy.

The GL-5 oil does indeed eat the synchro's, thats because its seeing a metal thats not supposed to be in your gearbox to start with.

The transmission companies are therefore at fault for using "censored" parts but are trying to transfer the blame to the oil companies.

This is far more likely than the GL-5 oil being at fault, the oil companies have too much riding on their product and do endless testing.

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Re: Don't use GL-5 oil in MR2 gearboxes

Post by shinny » 17/05/18 0:29

That's an interesting idea... sounds like a conspiracy theory, but my deteriorated box was rebuilt before I bought it. No idea if the parts were OEM or not.

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