Oils can sometimes be more controversial than fuel filters. But here are my thoughts on your question.
The Shell Rotella Synthetic (5W-40) is a Group III based product. Not really a synthethic but a highly refined petroleum product. The Mobil product is only a Group II based product (good, but not as good as a Group III basestock) The 5W-40 rating may be what is needed during the winter months in Ohio. (The manual shows use 15W-40 down to 0 deg F. and 5W-40 below that.) Not sure if it gets below that in Ohio during the winter. You may want to leave some margin though.
With regard to the additives in the oils, since the Rotella Synthetic product still has a "CH" rating while the Mobil Delvac 1300 is rated "CI", I suspect that the additives are more robust in the Mobil product. One of the main reasons for going from "CH" to "CI" is for the diesel engines equipped with a Exhaust Gas Recirculation (EGR) system. All California trucks like mine (2002 and newer) have an EGR system. Your Ohio truck does not. So a "CH" rating is sufficient, though if there are no other discriminating factors (like oil viscosity in this case) you should always choose the CI rated oil.
If you want to read up on oil products, the following is a good website:
http://theoildrop.server101.com/ubb/ultimatebb.php
If given the two choices you mention and living in a cold winter environment, I would choose the Rotella for the winter months.
A fully synthetic Heavy Duty Diesel motor oil (group IV basestock) is the Mobil Delvac1. This product is not available at retail locations and is higher priced. However, it would give you the best protection on cold start-ups in the winter months. You can obtain the product at AVLUBE, an advertiser on this website.
Regards,
Alan
And on edit: I run Mobil Delvac1 year around also. While a cold winter night in So Cal is 40 deg F
, during the summer months while going boating to the Colorado river, it can get to 115 deg F. I like the protection that Delvac 1 provides.
Edited by: OC_DMAX