I have an 08 FX4 Screw with 62k on the odometer. I live in Nashville TN so severe cold weather is NOT an issue. I am hearing the slight "knock" sometimes when the truck is running. it isn't often but it has me concerned. should I be using the recommended 5W-20 that FORD recommends.... I have made some performance upgrades, BullyDog GT, CAI, dual exhaust and throttle body spacer. I run the Performance setup on the Bully Dog GT and run Premium gas. Do I need to make the switch to Synthetic? Synthetic Blend? go to 5W-30 etc....I love my truck very much and want to make it last a lifetime. I don't just want opinions here guys I need cold hard scientific facts.

any help and advice would be great, pre-thanks for help

 

5w20 Motorcraft oil is just fine. I personally have been using Mobil 1 Extended Performance 5w20. Only real reason is that due to how little I really drive, I only have to change my oil once a year and I know Mobil is good stuff. Also, ditch that paper weight of a throttle body spacer. It does absolutely nothing for you.