I just bought an 02 wrangler sport. It has 160,xxx miles and Im going to change all the fluids. I went to oreillys and they printed out a chart that had all the fluid recommendations on it but for the diffs it says 80-90, and 75-140. Which one do I need to use and does it need to be synthetic or not. I was also thinking about putting half a quart of Lucas in each just because of the mileage.