How about a little more information?
As far as the knocking and pinging:
Which car is doing this? (Between the two on your signature, carbureted vs fuel-injected?)
Does it happen at all engine speeds? Load or under load?
Cold or warm engine?
Have you filled up again with a different brand or grade and still get the same results?
Any recent tune-up work done?
Does it overheat?
Answers to these questions will help pinpoint the cause...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car