Gearbox Oil - which Spec. GL4 or GL5

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portculisz4

Member
About to do a gearbox oil replenishment on my 2004 E85 2.5i and confused as to which oil spec. I should use. I have read the oil should be 75w80 GL5 spec. but an interesting article I have just read says you shouldn't use a GL5 spec. oil in the gearbox, only in the Diff. According to the article the sulphur/phosphorus EP additives (used for high pressure friction situations more prevalent in a Diff.) in GL5 can react with copper and bronze materials and hence cause problems with the synchromesh rings in the box, you should only use a GL4 spec. oil instead.
(see article https://www.rymax-lubricants.com/updates/the-differences-between-gl-4-and-gl-5/)
Anybody know more about this ??
 
I have never heard the reasoning, but I thought it was pretty standard to put GL4 in the transmission and GL5 in the diff. Its what I've done and have had no issues (yet) :P
 
portculisz4 said:
About to do a gearbox oil replenishment on my 2004 E85 2.5i and confused as to which oil spec. I should use. I have read the oil should be 75w80 GL5 spec. but an interesting article I have just read says you shouldn't use a GL5 spec. oil in the gearbox, only in the Diff. According to the article the sulphur/phosphorus EP additives (used for high pressure friction situations more prevalent in a Diff.) in GL5 can react with copper and bronze materials and hence cause problems with the synchromesh rings in the box, you should only use a GL4 spec. oil instead.
(see article https://www.rymax-lubricants.com/updates/the-differences-between-gl-4-and-gl-5/)
Anybody know more about this ??
Click to expand...

API GL4 is what you want, 75w-80 or 75w. The whole reacting with yellow metals is a bit misleading these days at best in my opinion. Once upon a time the EP additives used to make GL5 did indead cause problems with yellow metals. But in the developed world these additives were dropped in the 1960's. Today, API GL4 and API GL5 use the same EP additve, the difference being GL5 has about twice as much of it. This means that it can have an effect on some synchromesh performance, too slippy if you like and can lead to a difficult shift and the grinding of gears, this then can leave yellow metal particles in the oil (synchros) and when drained out this can be mistaken for GL5 reacting with yellow metals, when it is generally cuased by wear.

In the UK, or Europe, stick to a good quality reputable brand and nothing will react with anything, it is just making sure you use the correct one recommended for the application for it all to perferm as it should.

Cheers,

Guy.
 
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