How come car warranty companies wont allow you to take a policy out on a car with 300,000 miles?

worthless troll question

Because they're in business to MAKE money, and a high mileage car (near the end of its life) is almost certainly going to cost them.

Same reason many Life Insurance companies charge substantially more to insure older people, and many have a cutoff age where you can't buy life insurance from them once you pass a certain age (because they assume you won't live enough years to pay in enough of a premium to offset a chunk of what they'll have to pay out when you die).

its on borrowed time

That's the same as having a life insurance company give you life insurance at 100 years old!

They would lose their *** and go out of business.

Because the car is already worn out and is practically worthless.

Insurance companies make money by managing risk. Income from new policies should be greater than payments made for claims otherwise they go broke. Business 101. A 300k engine has about had it, and no insurance company will warrant the life of it. Engine replacement or repairs - never mind the rest of the power train - are gonna be several thousand dollars, and over the few years these policies run for, it's very likely the motor will need work. So long story short, it's not worth the risk.

The warranty is for the first 100,K so it is all used up.

With that many miles the car will be costing more than they could possibly charge for coverage.