Don't use GL-5 oil in MR2 gearboxes

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

Post by jimi » 17/05/18 1:47

I think more research needs to be done on this, there's a lot of conflicting info out there about GL4/GL5 gear oils, for instance this taken from a the manufacturers description of a 75w90 gear oil
This is a GL-4 and GL-5 Specification synthetic gear oil meaning it is safe for use where yellow metals are present. It contains a buffered sulphur EP additive which helps protect yellow metals found in some gear boxes.
I also find it odd that Mr T would recommend a multi purpose gear oil GL-4 or GL-5 (even for the MK1 gearbox) if GL-5 wasn't suitable.
I've had Castrol Syntrax 75w90 Universal in my MK1 gearbox for well over 10 years (13 to be accurate) never had the slightest problem and the gear changes are as slick as when I got the car, maybe I've been lucky, maybe not, as I said there's a lot of conflicting info and stories out there.


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

Post by MR2DI4 » 17/05/18 5:30

jimi wrote:
17/05/18 1:47

I've had Castrol Syntrax 75w90 Universal in my MK1 gearbox for well over 10 years (13 to be accurate) never had the slightest problem and the gear changes are as slick as when I got the car, maybe I've been lucky, maybe not, as I said there's a lot of conflicting info and stories out there.
Well lucky from the point of view you chose Syntrax like me, but not lucky that that particular oil doesn't eat your gearbox because its not eating mine either.

Its going to be next to impossible to do the research if it takes 8 years to stuff the gearbox, by that time the car is usually bought and sold and nobody will know the service history, what oil was used let alone if the gearbox has been rebuilt or not.

If your worried I suggest just go for a GL-4 and change it every few years because NOT changing it does as much damage as the oil eating it anyway.

The oil should look as clean when it comes out as when it went in, in fact as I have posted before I have REUSED the oil in an older car gearbox. If you store it for 6 month, all the crap settles out and sticks to the bottom of the container so if your pour it off carefully and discard whats in the bottom its still a whole lot better than an oil thats been in a gearbox for 20 years or just use it as a "Flush" to get rid of the non sythetic.

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

Post by jimi » 17/05/18 9:47

Nothing to stop more research on the GL-5 debate being done, the 20mins on the internet I spent was enough to throw up a host of conflicting info/stories, hence why I suggested more research needs to be done.
As for reusing used oil :no: without taking a sample and getting it analysed I wouldn't even consider it and wouldn't suggest anyone else does, apart from anything else for the price and frequency its needs changed it makes no sense not to replace it.
Am I worried? no, if it was going to affect my gearbox I'm fairly sure I would be seeing symptoms by now, am I interested? yes, it would be nice to have more definitive answer to the debate.
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Re: Don't use GL-5 oil in MR2 gearboxes

Post by MR2DI4 » 17/05/18 18:05

Still going to be tough to get anything definitive. How do you know if the oil stuffed the box or that the cause of failure was just plain insufficient oil changes ?

You would have to get the oil analysed and you would also have to ID the source of the synchro's so basically its impossible and no ones going to do it.

The only test is time and owning the same car for like 20 years and then you can state for sure that with the OEM gearbox and an oil like Castrol Syntrax, because thats the ONLY oil thats ever been in it appart from the heavy shifting factory crap I took out of it over 18 years ago that this combination is faultless if changed every 60,000km.

If you have only had the car a few years, your screwed. Change the oil straight away to a GL-4 and cross your fingers.

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