You will not turn 300,000 miles for about 4 years. You will be 76 by then. Will you still be driving? I hope that your eyes, reflexes, and clear mind will continue well past 76, but it is something to think about, too. I’d keep the Regal. Or I could sell you my low mileage 1998 Regal (128,000 miles)! It runs well, too.