It’s amazing what a little internet looking will do. The back story is for my first fluid change I used some expensive fluids, cost was over $100 to change oil, diff, gearbox and final drive. It’s about time to do it again so I decided I would do some research and see what others are using, while doing this I decided I needed to understand what 75W-140 meant in the first place.

Who knew the W stands for winter not weight, all I have ever heard was 75 weight 140. Who knew the 75 is the viscosity rating at 32 degrees and the 140 is the viscosity at 210 degrees. Didn’t know that gear oil and motor oil might both say ?W-? but there done on different viscosity ratings so they can’t be compared just by numbers. Heck 75W gear oil is comparable to 10W-30 motor oil in viscosity.

Of course the numbers 75 and 140 still mean little to me, I looked over the viscosity rating chart but since I don’t understand the test info there’s little value there. My one take away is the smaller the number the more viscous the fluid is at the test temp so 10W is runnier the 20W at 32 degrees and SAE 90 is runner the SAE 140 at 210 degrees.

Guess I can say I learned something new today.