Can I use Valvoline Premium Blue One Solution Gen2 10W30 in my 1995 Cummins 12 valve in my Motor Home or do I need to stick with 15W40 engine Oil? Oil gets changed when Blackstone labs recommends that I change it, so far about every 5-6 years. 17 Quarts is a lot of oil to change annually when the lab says it is not needed. Being that this is an old engine I want to clean it up, but I am worried about the lower viscosity in an engine recommending 15W-40 oil. Any thoughts?