I HAVE A 2005 F150 WITH THE 5.4 L ENGINE. 6000K MILES. IT STATES THAT I SHOULD USE 5W20, BUT IS THIS THE BEST OIL FOR THE ALLROUND GOODNESS OF THE ENGINE. I AM NOT WORRIED ABOUT THE WARRANTY.
Good thing you said you are not worried about the warranty... otherwise. I have seen this motor with over 200,000 miles on 5w20 Motorcraft, with no oil related failures.
I have also seen this motor with 150,000 miles on Valvoline 10w30, with no oil related problems.
I put myself at great risk by recommending Valvoline Durablend 10w30 but anyways one must sometimes live on the edge.
Yes, BUDSHAD...stay with the 5-20. If you are not concerned with the warranty use a fully synthetic 5-20 oil and a very good oil filter and extended OCI's...
Here's the best used oil analysis evidence I've seen that indicates that oils thicker than the recommended 5w20 don't provide any additional protection in Ford Modular engines.