I have the 2.7 turbo,my engine oil is 10-40,which an oil company and my mechanic reccomend,only put fully synthetic in if you are going a long time between services.
Fully synthetic oil ( contains extrat additives ) is the choice for engines that have been ' designed ' to be used with it from new. I've always found that an older engine that has been serviced regularly using a semi synthetic blend will tend to leak slightly when using the fully synthetic variety.
Some may disagree, but that is my personal findings.
Lest we forget we ran spits and hurricanes etc on essentially mineral oil !