I myself am fully in the camp of driving old vehicles and aim to be mindful of minimizing pointless consumption.

HOWEVER, I would argue that your humblebrag about the age of your cars, right after your friend talks proudly about his new Porsches, is the far more odious of the two boasts.

Conspicuous asceticism carries with it projected moral superiority, and it seems clear you are opening judging your friend's buying choices as inferior. It's his money, and his happiness. And I notice you can't help but add a final coda/dig that you are much richer than your friend.

I'm only sensitive to the pitfalls of your mentality because I was raised to handle money in the same way as you, and have to fight the urge to be obnoxiously gleeful about, for example, my low housing costs when conversations about rent come around.