0-20, 5-20, 0-30, 5-30 please help out a confused soul

[markrb]

My 03 V6 calls for 5-20 oil. I have read here and recently started using 0-20 oil. However other members I see are running 0-30 or 5-30 in their cars with the same engine. Is there a rule of thumb as what is best and I think I heard some people believe changing based on the time of year?
Until a couple of months ago I only used 5-20 as that is what my manual says to use, but the more I read here the more confused I get.
Don't even get me started on synthetic, synthetic blend or Dino as that one is also very confusing.
My goal is I need my car to last. It has 180k on it now and has run pretty darn good. Any possible fuel savings or longer interval oil changes are gravy when compared to my main need of extending the life of the engine.

Please help a confused soul out.

Thanks,
Mark

[Jake07V6]

Use Val. maxlife 5-30 I don't think it comes in 5-20 but I may be wrong.

[RTexasF]

5W20 is perfect so stick with it. 180K on the clock should tell you something.

[stevencrosbie]

5-20 is the choice to stay with!

Don't change what works!

[Trip]

Agreed. Stick with 5-20.

[Ice]

Stick with 5w-20 and dino oil. Switching to synthetic at 180K is highly not recommended.