I just replaced a 2005 4.3 at 176,000 miles. I am the second owner and I knew the meticulous first owner. He had lost an oil pump and a timing chain during his tenure. For a good while it had a broken or weak valve spring that would dramatically limit the performance at 94 mph. Various other operating issues, low -ish compression all around and finally #6 showed 10-12 psi compression. I pulled the plug at that point and replaced the original engine with a $500. used engine from a yard I trust.
So apparently there is at least one which refused to run forever.
The rest of the truck is nice but the original 4.3 engine wasn't quite up to par somehow.
CJE
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Originally Posted by 901Memphis
I think the 4.3 is the exception, it runs forever on anything, any flavor. I don't think i have seen one of these engines that didn't outlast the rest of the truck.
I think recommending any API SN 5w30 is appropriate.