2007 when I got my learner's permit as a teenager. I immediately got placed on oil change duty and basically was free to throw any oil in the cart at Wal-Mart for our cars. In my mom's 2001 Ford Taurus with the 3.0 Vulcan motor I tried pretty much every mid-priced synthetic around (no Royal Purple or Mobil 1 Annual Protection) and would regularly change synthetic out at 3000 miles religiously. Between said 3000 mile changes it used almost no oil. I didn't know about the synthetic causing leaks in vehicles ran with conventional thing until relatively recently. My favorite running oils were Valvoline and Mobil 1 0W20. I read about 0W20 in some sort of Import Tuner or similar magazine back then and just had to try it out, haha.
Weirdly, though, as a comparatively old man, I'm much more likely to just use conventional or synthetic blend in stuff. One vehicle I owned, a 1997 Galant, I used a NAPA Gold filter and Supertech conventional (not even high mileage, just normal green label conventional) 5w30, and ran it this way for about 40K miles. It would use almost no oil between changes at 5-7K doing this. I switched to conventional in it as money got tighter and I stopped having my cool Import Tuner dreams and viewed the car just as an appliance like "adults" do. I was pretty religious with PCV maintenance and would spray the valve out once a year or so with WD40 or brake cleaner, and there was only light varnish on the head when I pulled the valve cover off.
However, towards the end of its life, I got a bug up my ass to use Rotella HDEO synthetic blend 10w30 for a few oil changes, and shortly after it started leaking a lot more and developed a major front crank seal leak. That eventually spurred me to sell the car, since it would leak a quart every 10 miles or so. I can't say for certain the oil choice alone was the reason, but now I'm hesitant to use synthetic in stuff. Even my mom's Five Hundred, I ran a Valvoline synthetic 0w20 in it once and it leaked quite a bit more compared to the Motorcraft 5w20 synthetic blend I normally used.
So, a story of someone converting back to dino, haha. I do like how synthetics run for sure, and do notice a smoothness difference usually, but now I err on the side of caution. I don't think I've ever taken any oil change beyond 7000-8000 miles based on how black the oil gets and the difference I perceive in engine smoothness, I'd rather go conventional/syn blend and just change it more often.