My 2012 gasser started squeaking after I washed it two weeks ago. It dried and stopped, I washed it again, and started squeaking again. Takes about a full week to diminish. Got an appointment at the dealer tomorrow morning, but some investigation revealed a loose idler. Even with a tensioned belt on it, I can move it slightly by hand.
2012 Chevy 2500HD ECSB, 6.0L gas, auto, 4x4, LT
2003 F450, 7.3L PSD, 6 spd stick, 2wd, dump truck
1983 GMC K2500 pickup - working on a Cummins 5.9L swap
1987 GMC K3500 Dump, 6.2L diesel, TH400 auto - project plow truck