Check the maintenance schedule for your vehicle (it's in the owner's manual or a separate booklet) to see what the manufacturer requires. Chances are everything you need could be done at a competent repair shop that is more convenient or less expensive than a dealership. Don't assume, however, that a dealer will always be more expensive. They may charge $40 or less to change the oil, rotate the tires, inspect the vitals and throw in a car wash.
It is important that you recognize the difference between an EIN and a DUNS number. Although the EIN number is used to report and pay taxes to the IRS, it is not used to establish credit for your business or to report your credit history to the credit bureaus.
But I have several DUNS+4. I use a separate bank account for each contract, and that calls for different DUNS+4 numbers on each bid or proposal. Different DUNS numbers may or may not correspond to different segments. But every speck of data in the CCR database is tied to a specific DUNS number, not multiple ones. The same data can be put in multiple records for multiple DUNS numbers, but whatever you do or look at in CCR, it applies to one record at a time.