That is one of the funniest things I have ever read here! LOL! Seriously, the only time my car ever 'pinged' was on Citgo. I suepected them of watering it down.
There's a reason that the stations were referred to as something very similar-sounding...Schidtgoe, or something like that :>).
Good riddance, Chavez. Go hawk your crappy gas somewhere else.
You won't get to the water until your tank is mostly dry. Venezuelan crude is about as low grade as you get. Hence the most likely reason for the knocking.