Oil for differential gears
Oil for differential gears
(OP)
Hi!
I've got a Chinese light truck, in its rear axle differential service manual it says "Use 85W-90 GL4 oil". In the repair shop I have 80W-140 GL-5 oil, so I decided to use it. The enviromental temperatures here is around 30° C average so I think the viscosity difference is not an issue. Since there are not "yellow metals" such as brass or copper in the diff, think it will be no problem with GL5 instead of GL4.
Please your comments and suggestions about my decision.
Guess I'm still learning.
Thanks!
I've got a Chinese light truck, in its rear axle differential service manual it says "Use 85W-90 GL4 oil". In the repair shop I have 80W-140 GL-5 oil, so I decided to use it. The enviromental temperatures here is around 30° C average so I think the viscosity difference is not an issue. Since there are not "yellow metals" such as brass or copper in the diff, think it will be no problem with GL5 instead of GL4.
Please your comments and suggestions about my decision.
Guess I'm still learning.
Thanks!





RE: Oil for differential gears
RE: Oil for differential gears
replacing the 85W-90 viscosity with a 80w-140 is a different matter. a 85W-90 can be regarded as a 90 with a guaranteed low pourpoint, the viscosity at operating temperature will hardly differ from "just a 90".
a 80W-140 however is a less temperature sensitive oil that includes a viscosity index improver to make it less prone to viscosity change when the temperature varies. that means that in actual service it more or less behaves as a 140 oil with a much higher viscosity then the manufacturer anticipated or deemed necessary. it also means operating temperature may well be higher due to churning losses resulting in a somewhat higher fuel consumption. thus, the oil is more viscous and that may also lead to problems with foaming.
if a 80w-90 is unavailable i would rather prefer a 90. it will be very hard to find a 80W-90 GL4 anyway, most if not all of the available 80W-90 oils are GL5, whereas most of the GL4 oils are 80W.
RE: Oil for differential gears
RE: Oil for differential gears