My 69 year old dad purchased a lightly used 2013 TDI Passat in 2013 for $30k. In addition to the Passat, he kept his old Acura MDX to tow a small boat, and to have an AWD vehicle when needed in the winter months. It was dumb to keep the old car, as there isn't a day in the year that the Passat couldn't get him to work, albeit more slowly, and my mom's Acura RDX could have towed the boat, not to mention all the additional repair/insurance costs the MDX brought during this time. Now, with the boat, AWD and his preference for SUVs in mind, my dad wants to get rid of the Passat and buy a used Toyota Highlander (probably for about $30k). He thinks the Passat was a mistake.
My parents are 65 and 69, and aren't retired. Mom is in real estate and my dad is an attorney. I'm not sure they're even able to retire, which makes me all the more worried about a car purchase (and my mom wants a car too!). In my dad's defense, he's always purchased almost new, used cars and drives them for 10 - 11 years - not ultra mustachian but not awful. If he does this, he's going to take a double hit of depreciation over a short time and damage his chances of ever retiring (I think he'll probably work until he dies).
What are some things I can tell him to help him realize what a dumb financial move he's making?