On Mon, 19 Dec 2011 18:03:11 -0800, Steve Barker
wrote:

On 12/19/2011 3:32 PM, wrote:


It was NOT Multi-Vis oil that killed your cam, it was a defective cam.
It was not an unheard of problem

ACTUALLY, it WAS determined to be the multi-vis oil that caused the
failure. It was not the failure of the camshaft. It was determined
(very early on in the 6.9 days) that the multi-vis oils were reverting
back to their "thin" properties during extended idling periods.
(ambulance use was real hard on them) and what was happening was that
the oil was actually being over cooled and would cool to the point to
form condensation (while running) and the fine little needle bearings on
the roller lifters would RUST. I know , hard to believe, but then the
resulting failure of these little needle bearings would cause the roller
to seize, and consequentially, the cam would be ruined. My particular
vehicle was not an ambulance, but i never shut it off in the winter and
thusly had mucho idle time. Of course, my truck was an '85, (only 2
years into this engines use) and the official determination didn't come
out until about the same time as this failure. I've never used anything
except straight 30 in everything i own since.
OK, EXTENDED DRAIN on Multi-Vis - the MILEAGE was low, but running
hours were high. And using synthetic oil would have made the problem
worse, because synthetic oils are not as effective at reducing
corrosion. The ambulance use is EXTREME. A very extreme example of
SEVERE engine service. - and even straight grade oil would not have
prevented the problem , because the viscosity breakdown due to shear
failure of the long chain hydrocarbons/polymers in the VI Improvers
was just a small part of the problem.

You only told a very SMALL part of the whole story in the original
post - and you left out all the important stuff.

135000 miles of ambulance service is roughly equivalent to 500,000
miles of "normal" service - in some areas even more.