What's the difference between 5W-20 and 5W-30?

I gotta tell all you guys what a help this thread has been to me. My 02 EP3 has had a lifelong (132k) diet of Mobile1 5-W20 per the owners manual and lately I have been using their Extended Life varity, changing it every 5000 mi. I have an oil change scheduled this weekend and this time I bought 5-W30 based on this thread. Just a couple of weeks ago I did a solo (just me & my EP3) NM to MA to NC and back to NM loop of the country and put well over 6000 highway mi on it in a continuous trip. I burned 1 quart of oil, put in about 500 mi from home on the return. Not sure if it burned the whole quart, the front seal weeps a bit but doesn't leave a drop in my drive yet. I am making the tool to hold the front serpentine sprocket so I can replace the front seal.
Just wanted to say thanks for all the good info in this thread.

AceEngineer

So I never really cared about oil so I came here and I see this and been using 5w20 for like 10 years in my car but only have 60k miles is it to late for me to change to 5w30? And what's the best oil to get in this weight royal purple or something else? Also my head does make some louds noises tho prolly galling alote but I never rem the car always shifting at like 3k but anyways thanks for any advice