Quote:
Originally Posted by serialk11r
EDIT: Okay nevermind couldn't find it, but I'm not sure how much higher temperature say 40 or 50 weight oil can take and still maintain 20 weight oil (at more reasonable temperatures) viscosity, I have a feeling it's not that much.
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1) &&W-40 and &&W-50 oils, particularly with higher && of 15 or 20 can have much higher HTHS than 0W-20. And remember viscosity changes logarithmically with temperature, no linearly.
Quote:
Originally Posted by serialk11r
EDIT:
Also, thicker oil naturally picks up more heat as a result of increased friction, though I imagine this is not a big effect (could be wrong).
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2) It generates more heat due to internal friction and power required to move something thick.
Quote:
Originally Posted by serialk11r
EDIT:
The biggest argument for thicker oils that I've seen on BITOG is that sliding surfaces under high pressure (i.e. cam lobes) don't receive pressurized oil and so thick oils actually do protect them better, but this engine's valvetrain has rollers so it's not as big of a deal or something.
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3) Agree partly, except a large proportion of the protection for flat tappet sliding cam follower interfaces comes from the antiwear additive that will oxidize in the interface to form a phosphorous(in the case of ZDDP) protective layer.
ZDDP is also a very cost effective antioxidant whose function has to be taken over by other formulation solutions as ZDDP has been reduced.
Roller followers significantly reduce friction in this area. This design feature contributes to better fuel economy and/or power. It also allows other antiwear solutions that reduce phosphorus that is considered to have long term negative impact(via oil consumption) on catalyst life.
Like I have said before, engine oil formulation is a big balancing act of multiple requirements.
But I am probably suggesting things more complicated again!
