Any Difference Between 75w-90 and 75w-85?

[Hot_Ajax]

My 4WD truck calls for 85 in the front axle and rear diff, and then for -90 in the transfer case. Would it be safe to just get a case of the 90 and use it everywhere? Seems absurd to be buying all those single bottles for 5 points of viscosity. Thanks.

 

[Greasymechtech]

For best MPG, use a 75w85.

I'd use any of the name brand full synthetic GL5 75w90.

I was NOT too impressed with fluid condition and drain plug magnet contents when running the 75w85.

 

[CT8]

You will never see any difference between the -85 or the -95. Thicker gear oil is better.

 

[Chris142]

Not enough didference to matter

 

[Jetronic]

availability and price might be better for the 75W-90?

 

[stchman]

I am not a gear oil expert, but I HIGHLY doubt there is much difference between 75W-85 and 75W-90.

Mobil 1 75W-90 can be had at most auto parts stores for about $10 a quart.

 

[Hamburgler]

Imperceptibly lower mileage with 75-90 all around, but slightly better cushioning between the pinion and ring gears in the differentials. Go for it.

 

[MolaKule]

Originally Posted By: Hot_Ajax
My 4WD truck calls for 85 in the front axle and rear diff, and then for -90 in the transfer case. Would it be safe to just get a case of the 90 and use it everywhere? Seems absurd to be buying all those single bottles for 5 points of viscosity. Thanks.


The front differential doesn't get as much use or loading as the rear differential so many manf. are specifying 75W85 to get less viscous drag for that .1% better CAFE figure.

Use a good synthetic 75W90 in both differentials.

 

[Hootbro]

My understanding of calling out 75W-85 over 75W-90 is to ensure a synthetic gear oil is used.