I was surprised to see the Winchesters driving everything but their 4 dr Impala in season 7 of Supernatural... but though they drove a Mustang, a Riviera, and a Pacer... I never expected a cool 70 Charger and a 69 Road Runner

It turns out that they made a plot point about locking the Impala away for season 7, though I don't know if there were production issues behind the storyline that the Leviathans (disguised as Sam and Dean) go on a killing spree (while driving a 67 Impala) causing the real Sam and Dean to become America's 2nd most wanted criminals so they lock up the Impala to avoid detection.

https://supernatural.fandom.com/wiki/The_Impala#:~:text=stole%20the%20Impala.-,Season%207%3A,a%20new%20car%20every%20week.