HELP I need a reliable used car

I appreciate your perspective. I drive about 40k miles a year for work. I chose the diesel because of that. Before the fix that Volkswagen did because of their fraud they actually worked very well. Is it even possible to live without debt in today’s world? Everything is so over priced and totally disposable.
No debt? Yes, it takes self discipline and personal responsibility. We even paid off our mortgage. Most would agree that it's understandable to have a mortgage, though. If you can pay for it (whatever it is) monthly, plus interest, you can save for it monthly and have cash when needed. Google, "Dave Ramsey". Very helpful guy.
It doesn't help you now, but I learned years ago that getting good mileage is only part of the game. It has to be cheap and (preferably) easy to fix yourself. I knew a guy in the mid 80's who had a Ford Fiesta. He bragged about the 30 mpg while I got about 16-17 with my slant. He needed an alternator and it cost him some outrageous amount of money. Luckily, his BIL installed it for him! Savings on gas right out the window for the alternator! I only did auto mechanics when I was young, but what I learned has saved me THOUSANDS (there's that "SAVE" word again) over the years. A man I work with had to get rotors and pads. He said something like $5-600. I told him I just bought the same parts and did the job myself for about $90. Maybe you do stuff like that yourself, too. Point is there's a lot of ways to save money without being cheap.