I have a friend on FB who said he did the same thing, minus the verbal agreement, and made sure the loan didn't have a pre-payment penalty. He then paid it immediately, which I assume led to a strong talking-to for the employee that authorized that sale.
He held up his end of the deal, paying 18% interest on a massive truck loan for 3 months.
The sad thing is many people would do the same thing without the ability to pay it off in full. At that interest rate and a ~7-10 year loan term, you'll be upside down on the vehicle until the very end of the loan. And most people wouldn't keep the vehicle that long because something else changes in their life...or they just want a newer vehicle.