Ford 5.4L 3V engines produced from 2004-2008 (or up to 2010) are known for cam phaser issues. A cam phaser is a mechanical device that changes the valve timing depending on engine rpm. They are activated by oil pressure through a solenoid and oil path into chambers inside the phaser. With the engine warm, they have a tendency to "clatter" from 800-1300rpm on these year's engine. 160 pages of info Some companies make a lockout for them to get rid of the noise and potential damage that can result if they fail: livernoise lockout I bought a used 2009 F150 with this engine 1.5 years ago with 70k miles on it. It now has 93k miles on it. We use it to tow our travel trailer and other longer trips without the trailer as well as being driven to work 2-3 days a week. This truck has no actual phaser problems, but I want to keep it that way. The engine is inherently noisier than most, but runs well and has been maintained. I have tried the following oils over the last 1.5 years: mobil 5w20 mobil 5w30 QSUD 5w20 PP 5w30 (old formula) PP 5w20 (old formula) PP 5w20 (new formula) 70% mobil 5w20EP, 30% mobil 0w40 70% TGMO 0W20, 30% mobil 0w40, 150ml LM moS2 As you can see, I've been hunting around a bit. I can't get ford 5w20 semi-synth as easy as I can get the other oils, so I haven't run that. I suspect the engine internals will never have a problem, but as far as the noise from the phasers (the lock/unlock pin clicking and limiting vanes smacking against their stops) goes, they are quietest with the mobil 0w40 blends. I actually can't can't hear them even with the oil at full temperature with the last two blends. They clatter terribly with any of the PP in the sump (5w30 or 5w20) and to varying degrees with the others. My hypothesis is that it has something to do with the group 4/5 contents of the mobil 0w40. Both blends seem to be in the 30weight range when hot, but a regular 30wt oil seems to clatter anyway. I know I am totally over-analyzing the phaser noise, but am interested in other's thoughts.