.....jerry cans are NEVER laid flat....they all leak and those cans would be draining oil into the engine compartment. Sandbags on the fender? Pershings did not use them, and why on the fenders....to protect the tools?
As far as jerry cans go you are most likely correct, but don't tell that to the guy that stashed one in the storage locker. The "Sandbags" are a rolled up vehicle tarp.
Both of the images are from The Pershing/Patton in action from Squadron Publications. One of the few sources I've found for Pershings in WWII.