I have a 2001 Chevy Silverado 1500 Ex-Cab Stepside 4x4 with the 5.3L It's just turned 50,000 miles and I'm only putting on less than 6K a year lately. I've just finished changing all the fluids on both diffs, tranny, transfer case and I am about to change from dino to Pennzoil Platinum and would...