I'm about to change out my dif oils and in searching for "80w-90" gear oils I see Mobile-1 only makes 75w-90 grade, but they also make something called Mobilube HD Plus 80W-90. It's not synthetic like the Mobil-1 but it is supposedly extra heavy duty and made for commercial applications, but can also be used in light trucks and cars. Especially for "off road" vehicles that take more abuse.
Is anyone using this HD gear oil?
Does it matter if I "stray" from an 80-90 oil by using the 75-90? Am I better off with synthetic in the "wrong" grade? I'm a bit lost here, just trying to do whats best for "old Betsy".
So before I lay out all that cash in a day or so I need some help. Thanks.
.
- Heavy duty manual transmissions, axles, and final drives requiring API GL-5 and MT-1 level performance.
- On-highway light and heavy duty trucks, busses, vans, and cars.
- Off-highway industries including: construction, mining, quarrying, and agriculture.
- Other heavy duty industrial and automotive applications involving hypoid and other gears operating under conditions where high speed/shock load, high speed/low torque, and/or low speed/high torque conditions prevail.
Is anyone using this HD gear oil?
Does it matter if I "stray" from an 80-90 oil by using the 75-90? Am I better off with synthetic in the "wrong" grade? I'm a bit lost here, just trying to do whats best for "old Betsy".

So before I lay out all that cash in a day or so I need some help. Thanks.
.