2009 Ford E-150 (NOT a Transit!!!), 4.6L engine, currently at 401,892 miles.

Oh, just so proud of myself! Changing the oil (Mobil 1 Full Synthetic High Mileage) and filter on my own (probably the easiest thing I've had to do on it so far). I don't think I spilled more than 2 ounces of oil. Got the nice Fram Synthetic Endurance FE2 filter AND a new MAHLE oil filter plug gasket.

Everything seemed fine. No leaking at the plug or filter, it even sounds quieter! (Sad note: I seem to have maybe never checked the oil level, relying on the window sticker for when to change it, it was down to the bottom hole on the dip stick and only about 5 quarts of oil came out.). Even with 6 quarts, though, the oil level is only half way between the low and full marks.

Question 1) Should I add more oil or is "right in the middle" just perfect? ANSWERED: Owners manual states that if the oil is between the marks "DO NOT ADD OIL." Okay! Stop shouting at me, Ford!

Question 2) Upon finishing, while doing a bit of cleaning under the hood (as if it matters!), I finally notice the red and white sticker under the front right edge of the hood:

USE ONLY 5W-30

I used 5W-20 because that's what it says in the service manual (and, to lesser authority, everywhere else on the internet

Did I mess up?

Do I need to dump 6 quarts of brand new oil (that is not appropriate for any of my other vehicles) and run out and get 5W-30????

Is there some advantage to 5W-30?

I'm inclined to just "send it" as-is.

Thoughts?