I have a 08' Silverado with a 5.3L AFM with 72k miles. I use Mobil 1 5w30 and ac delco filter. The truck has a loud ticking noise when it starts, it does not do it all the time but is getting worse. I took it to a dealer they had it two days and found nothing wrong. Five days later it was so loud I recorded it on my phone which lasted two minutes while the truck idled in my garage. I sent the recording to the dealer over a week ago and have heard nothing. U The noise gas gotten so bad that you can hear it in the cab as you drive down the road and lasted a whole 7 minutes this morning. I have been around cars all my life, currently have an old Vette in my garage doing a frame off. I am smart enough to know there is something wrong but no one seems to care guess GM assumes if the engine makes it to 5 years or 100k miles they are off the hook. Very disappointing, I just want my truck fixed before I get stuck with the bill!!!