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Without looking at the hard number's, I can't imagine you will save a ton of money refinancing from your current rate, why not just start paying extra which effectivly lower's your interest rate anways? Unfortunately, interest rates are rising and will keep rising, you may find a better rate somewhere else to refinance with but it probably won't be a huge difference.
The lowest rate my CU offer's at the moment is 3.09% for up to 63mo's on a 2015 or newer for a 740+ TU auto 08 score, with the rate jumping to 3.69% on a 2014 or older.
DCU has published rates on their site of 2.74% for new or used up to 65 months (anyone can join).
NFCU offers 2.59% for late model used (2017, 2018, 2019) with up to 30,000 miles for 36 months OR regular used cars 4.29% for 36 months.
I like NFCU a lot, but both of my cars are financed through DCU at less than 2%, but those days are over. I don't think you'll find a 2% used car loan anywhere today.
You might look into joining DCU and from what I understand you can apply for the loan first and if approved then join.