"GL-1 mineral oil should be used in gear boxes with bronze parts."

Paul WNC

Here's a detailed discussion of your issue:

https://bobistheoilguy.com/forums/ubbthreads.php/topics/509692/1

When I raised this question with a lubrication engineer at one of the oil companies he told me that modern GL5 gear lubes are buffered to prevent adverse effects on yellow metals. He also told me that unbuffered GL5 oils of the past do have the potential to erode yellow metals but only at very high temperatures that are not reached in transmissions used in "daily driver" applications.

So this "No GL5 in synchronized transmissions" claim seems to be one where not all "experts" agree. The SAE has laboratory procedures for testing oils. The results of those tests are probably worth researching and very reliable.


Last edited by yar; 01/12/2017 2:20 AM.
Ray