Lio,
You are right it should be enough to follow the OEM recommendation, although
sometimes the guidance is not clear or the particular oil is not available.
The temptation to improve on the recommendation or "use the best" means
people look at a spec and see "meets or exceeds API..." and assume that
means it is OK for their engine, it might be or might not be, the point I
was making is engines are usually designed and tested with a specific oil,
in the real world they are filled with a wide range of oils, an oil meeting
the API spec stipulated by the OEM isn't necessarily a) exactly equal to the
oil used by the OME b) the best oil for the engine, on the other hand the
latest and best marketed oil might not be the best either.
I would imagine most million mile trucks were always operated on the same
oil and the oil was quite basic also the engine mechanical injection and
without exhaust gas recirculation and the higher engine temps found in the
latest engines.
On the other hand the Nissan 2.5 litres produces something like 140HP and is
a 16 valve with overhead cams, weighing 1/2 what my petrol Toyota 2F (4.2L
135HP) does.
I agree the oil used might not be the cause of the failure in the Nissan, I
did find some swarf from manufacturing present in the head, but wear in the
cam / followers is often oil related and as there was no sign of overheating
from lack of oil so the suspicion is that the oil broke down and provided
inadequate lubrication.
Malcolm Bagley
Stafford, UK
1975 FJ45 Pickup (In Work)
_______________________________
Now, when I say "using OEM recommended oil is enough", of course I mean
respecting the specs (API, ...)
Cheers,
Lio, Paris countryside, France
'92 HDJ80, getting ready for first African trip (Marocco april 07)
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