I am a believer in full synthetics. The first thing I did when I bought my 2002 F150 King Ranch Supercrew was take it to my Amsoil dealer and have him change everything to full synthetic......engine, rear end, transmission and transfer case. I now have about 165,000 troublefree miles on it.
One thing, when he took off the rear diff. cover....it was full of muddy water looking fluid.....it was ugly. I think we dodged a bullit on that one. I guess those assemblies must sit outside in the weather until they get installed. I was NOT impressed and hope that my new Transit doesn't start out in the same manner. And yes, the first thing I will due when I get my new rig is change everything to Amsoil full synthetic.