I have a 2006 ford Explorer limited with 96000 miles. You can see by doing the math we drive the car alot. Ford says I need to do a complete tune up. I change the oil, air filer, and gas filter often. I think the only thing I really need is just to change the plugs. My friend says their are no wires (he works for Ford parts). Ford says I need a differential service and fluid change. My friend says it is just a bull...is that true? Also how often should I do a coolant flush? thanks for the answer in advance.