i have a 2001 ram with astock diesel ,i've been using valvoline premium blue since it was new . okay heres my problem it's getting harder to find . i'mdown to one store and there always out , i found some oil at my local farm supply store it's called mystik jt8synthetic blend it's sae 15-40 and it exceeds api service ci-4plus, ci-4,ch-4,cg-4,cf/sl,sj and the doughnut says sae15w-40 onthe bottom ci-4plus . has any one heard of this oil? and would it be okay to run in the cummins,the bottle says it,s good for diesel engines and gas engines??? also i've read tdr on analysis of lube oil and the way i understand the ci-4plus is what i want for the older engine, is there any thing i'm missing or not understanding thanks for yourtime guys.