New 2015 3500 DEF fluid and other misc questions.
 

First ever vehicle I have owned that takes DEF fluid. Like oil brands and fuel qualities, are there any recommended brands of this stuff?

Oil. I have always used Rotella T 5w40 and the owners manual even states using Rotella T. I have been using Royal Purple in my other non-diesel vehicles and really like it. Thinking about using it but only comes in 15w40 and we are in winter here now. Thoughts? Not interested in Schaffers or Amsoil where I have to order it. I do like the 5w40 but I can't find Royal Purple in 5w40 for diesel. Am I missing it somewhere?
Also I have always dumped the factory oil between 500-1000 miles. Thoughts on this for this 6.7?

Seat covers for heated/ventilation seats. I did a search but the links don't cover the consol I have. Anywhere I can see actual pics?
As well, any steering wheel covers that are compatible with heated steering?

Thank you

I have 11,000 miles on my 14 according to the computer it's still good

As far as DEF, the brand may not be as critical as the age and spec to be sure it meets Ram manual requirements (as should the oil). Blue DEF is a common one available almost anywhere in 2.5 gal containers. Determining the age is a bit cryptic. As an example, there will be a number on the container like: PB171502354. The 17 means it was produced in 2016 (17-1=16). The 150 means there is 150 days left until it is 1 year old, the higher this number the newer it is. DEF degrades with time and temperature from about 6 months (hot) to 2 years or so (cool). Most sources seem to say it should be used within a year under most conditions.