Then howcome i have 125000 miles on my 99 WJ Grand Cherokee with the
straight 6, and often tow a 6500lb boat with not one problem yet?

Consider yourself a lucky man.

I'm on my second Jeep Cherokee, with 199,000 on it. My first had
195,000, and I wished I'd have kept it. I know many, many people with
the 4.0 liter 6 cyl. that have close to 200,000 miles and no troubles.
The one with 199,000 needed a radiator at 187,000.

Let me guess, none of them have ever burned any oil.

Right?