Hi. I own a 2005 3.7. I have owned it since 18k and now have 91k. I have always done my own maintenance and such. Now I KNOW with conventional oil my truck will get 3k miles before I notice power loss loud engine stuff like that, mpgs too. Now the last time I changed my oil I switched to a synth hoping for longer life better mpgs. Well I def got better mpgs but the oil did not out last the conventional any longer than normal. See from what I read, (i ride motorcycles and for anyone that's in a forum knows those guys are crazy about oil) everyone makes it seem like oil holds up to this and does this and that. See your oils might hold up to high temp and not lose its vicous properties, but it still gets DIRTY. All that dirt and byproduct from the air and combustion dirty the oil causeing the premature wear in parts. Also it breaks it down. Synth is a sham just like I always thought. You can't keep oil clean! Ill keep it in for the mpgs though.