I would like to update my experience with what I believe to be as close to the final answer as possible.

After replacing one vehicle and repairing the second only to replace the engine 25,000 miles later some things became very obvious.

1. Engine oil is critical, I had the shop put mobile 1 in ...

I found this thread while trolling the web about burnt valves. Some of you know that I'm the "OCTANE" monitor and we all want to prevent problems. Of late, over the past 2 years, I have heard several people saying that a motor was bad because of a burnt valve.

Most of us know that these motors ...

from LesII

My experience for what it is worth is that you will see reduced "off the line" and full throttle power loss using 87 octane gasoline in any 2.4 engine, however my gas mileage is exactly the same, after giving the computer a few tanks to catch up
my 1994 2.4 850 with 181,000 miles get 21 ...

From Les II

My experience is quite different, I have had burned valves on a 1997 2.4 non- turbo AND a 1999 2.4 Turbo
BOTH were purchased used--so I can only tell you I used 92 octane in them both. In this area we have very long steep highway grades the make non- turbos down shift for extended times ...