Guys I am new to your forum but I have been reading here for years. Here is the thing My truck has 5k on it and I used 5w-20 motorcraft full synthetic and a 820 motorcraft filter I have noticed a REAL faint knock at hot idle and the dealer said all the 5.4 have that low knocking sound, I know this engine has cam phasers and they do make some noise but this don't sound like it is top end noise but you know how sound travels in these modular motors. I would like to know if this is a normal sound for these engines?? I wonder if 5w-20 synthetic blend would be better then the full synthetic is this possible??? Next thing is would it be better the use a 820 ford race oil filer, It flows better the the stock filter right? I can but the 820 ford race filter for 10 buck from the dealer. I would like to see this truck get over 150k like my last truck. This is my first new ford truck, Thanks for the help guys..