I'v been dragging my feet getting all the necessary fluids for some maintenance work on my 2012 Jeep KK and 2003 Suburban, both four-wheel drives. Some of the fluids match up viscosity-wise, but not necessarily fluid type. For example, the older Suburban recommends 'synthetic' products for the front and rear axles but the Liberty states 'SAE 75W-90 Gear Lubricant' and 'SAE 80W-90 Multi-Purpose API GL-5 Gear Lubricant' as opposed to 'SAE 80W-90 Synthetic Axle Lubricant' for the Suburban. I've always assumed that in these types of applications, synthetic is acceptable. But I don't want to assume and then do long-term damage to any Liberty components. Your experience and recommendations would be appreciated! Thank you.