Decided o flush my power steering fluid in my 2500HD and I wanted to stick with the OEM synthetic fluid. I only had 60000 miles on my truck but the old fluid was quite dark and after the flush, it steered more easily and more quietly (the PS pump is quieter). I recomend a PS flush if you have high miles or if your PS fluid is obviously dark and contaminated. You know the old saying, an ounce of prevention is worth a pound of cure.