Im looking at selling my suv and buying an 08 Kning ranch but it has 329,000kms (204,431miles)and Im wondering how long I could expect the 5.4L engine to last

 

That's a tough call Depends on how it's been treated for the last 204K. One good indicator would be to get the seller to let you have a garage look it over, do a compression check and see how that looks,

 

It could last to 300k!?! I have a friend with on 04 that had 295k and was still running. I have a 2010 and mine had 235k and I decided to get a reman engine and in progress of doing some more mods to that engine but the 5.4 3v engines are good engines overall. They have quirks as any engine does. I would love to see some service documents before I would spend a lot of money on a truck with that many miles! Another thing to think about is the transmission... that vehicle has the older transmission before it changed in 2009 to the electronic style so I would be more worried about that!

 

From family and friends experiences I would say the 5.4 has already reached a point in its life when anything more is just a bonus. I've seen extremely well maintained 5.4s blow up inside of 100k and I've seen them last 400k and still going with what I would consider low maintenance for half its life.
It's a gamble. One that could pay off, the question is (are you a gambling man?)

 

Taking that gamble myself as original owner of very well-maintained 2007 F-150 4x4 5.4. The truck runs strong as mechanics that do some work here and there comment. It is approaching 170,000 miles. The ball joints were an issue not that long ago. We do drive a rough unpaved, high altitude road - but first time with ball joints replacement and had plenty of 4x4 F-150's for years. The a/c went out this summer when the compressor drove the engine down at idle to almost stalling. Also first time ever with an F-150 4x4. These are expensive repairs.

Not to be negative, but not sure these trucks hold up that well much past 200,000 miles. That is our goal with the 2007. It has been moved to secondary, 5,000 miles per year duty as we have two newer F-150 5.0 4x4's that feel very strong. You may be looking at one from a weak generation of F-150.

 

Good advice here. They can die soon or later like most trucks. The good ones can make 300k give or take with the right care. There’s always that one guy you know who never changes his oil but has 250k on the clock. If it checks out thoroughly and the price is right just make sure you are prepared to replace original parts sooner or later Like the Water pump, fuel pump, and any other parts that will prevent break down. Some of these things may have been replaced already. So it would be good to Know what parts of any have been replaced.

 

as others have said, it would be a gamble to buy that truck especially if you dont know its history. if the owner will let you, take it to a shop and have it looked over