I admit up-front that I'm not expert here, but I have a similar question, and I think you could imagine this as two possible alternative 10-year timelines. In one, you stick with the Ford and invest the $2000. After 10 years, that $2000 is worth about $3,250, assuming 5% return. In the other alternative timeline, you pay $2000 for the gas-sipping car, start off $2000 in the hole, but begin to put $100/month into investments. After 10 years, those monthly $100 investments accumulate, and you end up with $15,850, assuming 5% return. But, you put $2000 down to begin with, so your profit is actually $13,580 after 10 years (assuming you don't borrow money to buy the car). The delta between these two timelines is $13,580 - $3250 = $10,330.

The reasons not to buy the Toyota are (1) inertia -- if it ain't broke, don't fix it, plus it's a pain to negotiate and buy a new car, and (2) the Ford is a known quantity, you know it's been taken care of, while the Toyota is an unknown (though Toyotas have generally good reliability). Plus reason (3): whatever other reason you may have, such as you like the bigger car, etc. The question is, are (1), (2), and (3) worth foregoing a net gain of $10,330 after 10 years? 10 years is a long way off, so you want to know what $10,330 in 2023 is worth today's dollars. The present-day value of $10,330 in May 2023 is -- according to a calculator I found on the internet (use at own risk) -- $6,341.72, again assuming 5% return. So, to restate the question, are (1), (2), and (3) worth $6,341.72 to you today?

Anyone think I'm thinking through this incorrectly? I ask because I have a similar dilemma as the OP.

Edit: as I look this over, I'm not sure if I should subtract both the $2000 you put down on the car AND the $3250 you would have with timeline 1, or just subtract the $3250 you would have in timeline 1.