If you have 2 different gearbox oils that are the same viscosity and the same make then what's the difference between GL4 and GL5 oils? Noticed it today and was just wondering? Are they mixable?
- posted
19 years ago
Gearbox oil
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- posted
19 years ago
It's a friction rating thing, or something. Your gearbox will almost certainly take GL4 - usually GL5 oil is used in diffs etc.
At a push, you can use GL4 in something GL5 rated, but you can't do the reverse. If you stick GL5 into a gearbox, it can knacker the syncros etc. (too little friction for them to work properly).
But there's no reason whatsoever to use the wrong oil - the ratings exist for a reason. Look in your book, and see what it needs. Then use the correct fluid.
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19 years ago
Well my book says 75w90, but I seem to have aquired 2 GL4 litres and 1 GL5 litre, both 75w90. Now I've had time I've done some googling and I now know GL stands for Gear Lubricant, and the number represents to amount of Extreme Pressure (EP) additive, where the higher number basically means a more 'slippery' oil. GL5 is generally used in diffs, and GL4 in 'boxes. Guess I'll be trotting back top the Half and swapping them then! Mental note: read labels properly!!