How often do you need yo change your differential fluid. Is it best to go with synthetic or conventional. And what weight is suggested to be used on 4th gen V6's

 

your owners manual should give you the change interval. without looking at my own manual im gonna guess its 30K but may be 60K either way im a huge proponent of synthetics. they cost more but the cost per mile is about the same, as dinosaur based oils, if not better and thier wear resistent properties cannot be matched by conventional oils. the manual should also cover suggested weights of the oil based on the normal temperatures of the area its driven in. me personaly i like it heavy, like a 140 wt. but an 80-90 wt is just fine. youll find the synthetics will cover a larger wt spread (90-140wt for example) which is good and is due to the ability to custom tailor the oils during manufacturing kurt

 

The FSM calls for a lube change at the first 7500 miles only. However; for heavy duty applications,it calls for a lubechange every 7500 miles. 80W90 GL5 lubricant +4 Oz. of GM P/N 1052358 special additive, if you have limited slip differential.