Quick question... I see the RAVE says the transfer case takes GL-4 oil. The only GL-4 oil I can find in this God forsaken town is Lucas Synthetic 75-145 GL-4/GL-5. Is that okay for the DI in a pretty cold climate?

 

I'm using AMSOIL Severe Gear 75W-90 for the tc, axles/swivels. Worth every penny in the single digit degree weather and in summertime heat. Most will give their opinion on cost but I don't care, it's my truck not theirs and I get 18mpg even in the winter.

Lucas actually failed a few tests I found rather important like viscosity shear testing. Hey, if it's all you can get then I guess your stuck with it. 75W is rated for -40 and with it being synthetic it will not become a liquid brick. Unless someone lives in a severe cold clime they have no opinion to share with me about synthetics.

 

I am running the Amsoil gear oil as well on my D2, and their oil in the engine as well.

 

Oh, fear not... I am not afraid to pay for the best. I cannot find AMSOIL anywhere here, so my local choices are the Lucas or Royal Purple, but they are both 75-140 weight. The 140 sounds really thick; the high here is 19 today, and it's not even winter, so I am concerned that even with synthetic, the weight of the oil & forthcoming below zero temps may not be a good match. Perhaps I need to think about doing the 75 mile trek to the city to find something.

 

The 140 is after the oil warms up.

To make multi-vis oils they take a lower viscosity oil and add polymers to it that keeps it from thinning out as much when it warms up. So for example 75w140 starts out as close to a 75 oil and then only thins down to what a 140 weight oil would thin down to at normal operating temperatures. Normally 75 would thin down even more at temp.

 

So the 75/140 is a better choice, right?

 

Too thick for me but a few buds say it quiets their boxes. I don't mind listening to mine whine......

 

I run coastal 85-140 in the TC, diffs, and swivels. I buy it in a 5 gal bucket and change it frequently. Never had any issues.