I guess I need to search the YouTubes for "Survival techniques to light your car tire on fire." I honestly don't think I have anything in my car, this second, that could do that. How much heat does a tire need to light up? Is one of those mini-spares enough tire to make a good signal?

Its easy (well easier) with motorcycles, as you can readily get fuel out of the tank, assuming you have some fire source. But for a car? Not sure.

Mind, for this specific case, you have to appreciate that these folks were rather far from the beaten path. They were certainly far away from the local ranger stations and what not. Ideally someone may have seen it and reported it, but I wouldn't necessarily guarantee it. They were in a pretty large valley where this happened.

And, as an anecdote, my friends and I were stuck near there for 3 days one year. But it was in the mud, in the nearby dry ("dry") lake, and we were near a road. Never in any danger. But it was a fun extraction.

Clip one end of the jumper cables to the battery and short the other end across a small chunk of metal until it gets hot enough to ignite paper (or just spark them onto some torn up paper), add whatever else you have to build it up, add paper soaked in engine oil until that ignites, and then feed it with oil-soaked fabric and eventually shreds of tire until those burn readily, and then the whole tire (deflated first of course)

Just what I would try, not really sure if you could get it hot enough. Maybe a lithium battery would add enough oomph?

I thought about using the upholstery or plastic panels from the dash etc. but that's probably all flame retardant on any modern car.

I bet a road flare would do it. It's always useful to carry a pack of those.

Good thought but a rental car would definitely not have road flares.

The general problem is that even if you're a well-prepared person in general when driving to remote locations--you're probably not (and can't easily be) well-prepared when flying to a foreign country and renting a car.

Heck, forget the foreign country part. I'd be a lot more prepared for somewhere like Death Valley if I drove there from the East than if I flew there and rented a car.

I think some countries require you to keep one in your car.

Yes. Use the spare tire, not the car. The car may be your only source of shade or shelter overnight.

Yeah, I think advice is typically stay with your car, though probably relies on people knowing you're missing (easier to search roads than everywhere) or there being at least occasional traffic on that route.