My 01 Taurus with Duratec V6 wanted 5w20 as well. I used 5w30 once and noticed a slight decrease in fuel economy. Will I do the same for my Ram? Probably not until Asur runs it in his Ram and says it's ok
I'm averaging a little over 5000kms per oil change using full synthetic in my Ram. I am a die hard 5000km oil change guy. Dinoco for everything up until my Ram. Never an issue. Put 238,000kms on my 93 Explorer with the Ford 4.0L V6 POS. 10w30 changed every 5,000kms. It ran like like new (ie. like a dog) when I traded it in. I have an 87 BMW 325is. BMW says 20w50. That is all that has been run in that car (have documentation since 98) and it has 308,000kms on it and runs like a top. No leaks, no burning, have never had to top it off between changes. Also have an 04 Nissan Quest. 5w30 Dinoco every 5,000kms since new. Now has 175,000kms and that engine still purrs like a kitten. You can't hear that damn thing running it's so quiet. That 3.5 VQ engine is awesome.
I think if you run the recommended oil and change it often, your engine could last forever.