My own opinion is somewhat different, but the condition of your engine is the
important factor. If it is a well worn piece, with borderline bearings, the
thicker viscosity's may help maintain pressure when the higher operating
temperatures are reached.
If , on the other hand, your engine is in good condition, higher
viscosity's like 50 wt do not make sense. Oil is there to do 2 things,
lubricate & cool. You want a light viscosity oil at start up, so oil
will flow quickly & freely to prevent excessive wear. Once the engine
has warmed up, you want an oil weight that maintains correct oil
pressure & flows freely, both for cooling & lubrication. The engine
manufacturer has basic recommendations as to the type & weight oil to
use, based upon normal operation. You now have to adjust based on the
modifications you have made, but I somehow doubt you have increased
oil related clearances for a street engine. If this is a race motor,
we are beyond my knowledge.
Once broken in, I have run Valvoline, Castor Oil, or Mobil One, 10W30
in all my Buick/Rover engines with very good results, but these were
modified only slightly with up rated cams & increased
compression. When auto crossing, prior to the advent of Mobil One, I
did run Castor Oil 10W50, because of the high oil temperatures &
generally hot weather. Today, I might just run 10W40 Mobil One or
other synthetic. I like the synthetics because of their higher flash
points. Mobil One, as an example, will not start to smoke or degrade
until it gets to 370` F, while non synthetics are not good over 300`F
or less.
Jim Stuart
Simon Green wrote:
> HI
> I have a 3.5 rover that is outputting about 240BHP but I have a simple
> question. What oil should I use. I have been told as thick as possible?
> Simon Green
[This message delayed, as it needed manual intervention by the list
administrator. mjb.]
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