Personally, I don't know of any HYSA that is getting 3.9% interest or better. If it was me, I would just pay off the loan and be done with it. Then each month put that car payment back into your savings account to build it back up to the $18k. I went into hyperdrive back in 2020 paying of my remaining $16k of student loans that were only at 1.75% interest. Logically, it made more sense to invest the money since my interest rate was only 1.75%, but I really wanted them gone since I had been paying on them for years. The day I made the final payment and was able to print out the zero-balance statement I was overjoyed. I can't tell you how good you feel to have the debt gone. It has been almost 18 months since I have paid it off and I still get giddy, knowing I can say I paid off my student loans (I originally owed $48k).

But I also paid off my car loan 2 1/2 years early because I hate that kind of debt, so I am a type of person that will advise to pay it off. Currently, I have zero debt outside my mortgage and make plenty to invest these days. Sounds like you are doing the right thing living below your means. You can save that $7700 back up quickly with how you live.