Too_many_Cars,
The factory fill in your Dodge Durango is none either than Pennzoil Conventional (PYB) 5W-20. Chrysler has a factory fill contract with SOPUS.
And with PYB being the premier conventional (IMHO), Group II+ oil out there, you'll be hard pressed to improve upon it, with warranty considerations, and such. Yeah, you might see a little improvement in cold weather operation in Ohio with a move up to other SOPUS offerings such as QSUD or PP, but just a little considering the FF is 5W-20. And with extending the OCI out under warranty, very little else will be gained in "upgrading" to a synthetic.
I would continue using the Pennzoil, just like I recommend continue using Motorcraft 5w-20 in most Fords, as that is their FF, as well.
Take care,
Gary