I just bought a '99 QuadRunner 250 4x4 from the original owner's family. However, they could not find the owner's manual and I have front diff questions. I'm trying to replace the fluids to get ready for summer riding and I want to replace the fluid in the front diff. What weight of oil do I need to use in the front differential? Any specific brand that is better than others? It's going to be synthetic, I know that already.

 

80 weight gear oil

 

80 weight