harmbone2k2

iTrader: (1)

good stuff--bad stuff??

ferran586

If you read the stickies in this section you would find that it is actually one of the gear oils recommended for our cars. And for the record I just bought 5 qts of it to change my fluid.

swiora

The recommended Mobil 1 is GL-5, bust several posts state that only GL-4 should be used (per the manual). Who can shed light on this paradox?

jtacy

I read, perhaps on bobistheoilguy.com, that synthetic GL-5 (such as Mobil 1) is fine. It is the non-synthetic GL-5 oils that require sulfur additives (which are said to chew up certain types of synchros) to meet spec. I don't know for sure, but it is plausible and seems like a good place to start researching.

ferran586

If you go here you will find a line about half way down the page that states "Mobil 1 Synthetic Gear Lubricant LS 75W-90 can also be used in rear axles where API Service GL-4 lubricant is recommended"

jtacy

Some manufacturers will actually specify GL-5 oil for the rear axle and GL-4 oil for the gearbox. The problem with GL-5 in gearboxes is that it is thought to contain additives such as sulfur that can be corrosive to copper alloys such as those used in synchronizers. Rear axles don't have any such vulnerable metals. Now, some people have claimed that manufacturers put anti-corrosive additives in GL-4/GL-5 compatible oil to prevent damage. Tough call.

ferran586

Aaah. Ok. Thanks for little info.