5w-20 only ?

will i experience any problems using 5w-30 synthetic oil instead of 5w-20 synthetic my car was designed for ? its an 04 crown vic

Nope, it will be fine.

5W-20 was specified for emmisions and milage claims to meet epa standards. There really is no other reason to use it. The engine design has not changed over the years, just the programming and CARB standards. You can run any wieght oil AS LONG AS it meets the manufactures recommendations. I have run 0W-30 Mobil 1 in the 4.6 and 5.4 engines and never had a problem. I also Blackstone the oil to determine engine wear and they were all within standards.

yea i think ill go with 5w-30 mobil 1 wiht a motorcraft filter since its going to be warm here very soon.

We run 15w40 in all the Fords we have. Since 92 we have had no oil related failures that are common in the "real world". Haven't lost timing tensioners, cams, bearings or pumps. I am not advocating to vary from manufacturer specs, just saying we must be really lucky. We have the normal head leaking and gaskets, but no major problems.

We run 15w40 in all the Fords we have. Since 92 we have had no oil related failures that are common in the "real world". Haven't lost timing tensioners, cams, bearings or pumps. I am not advocating to vary from manufacturer specs, just saying we must be really lucky. We have the normal head leaking and gaskets, but no major problems.

What about the common oil burning these engines tend to do? Does the 15W40 help any? What brand? I run Rotella T in my F350 PSD, and I KNOW it is good oil, every blackstone test came back with outstanding results with high miles on each sample.