5W-30 vs 10W-30 start up viscosity

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what's important is the viscosity at 0 degrees c, or 10 degrees c.
by 40 degrees, they all extremely watery, and resemble oil. at 10 degrees the 10w30 is like honey.
 
Originally Posted By: scoobie
what's important is the viscosity at 0 degrees c, or 10 degrees c.
by 40 degrees, they all extremely watery, and resemble oil. at 10 degrees the 10w30 is like honey.


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At 15C, Castrol GTX 5w30 is thicker than Mobil 1 5w40.
At -35C, Castrol GTX 5w30 is almost TWICE as thick as Mobil 1 5w40.

So then one must delve into the differences between oils "5w" ratings and the differences in this area between conventional oils and synthetics.
 
I don't believe there can be any given answer to the comparison.
Conventional oil is a natural resource and by rights when something is natural has limits. Being a natural resource will react differently to different conditions, climate, work load, etc.
Sythetic oil is engineered from the ground up in laboratories with men in white coats- that formulated synthetic elements to act with oil like properties without the natural molecule breakdown of natural oil due to the extremes.
 
Umm, ok.

How about -30f? I just did some numbers for a post, RTS 5w-40 was 6800cP at -30f while PP 10w-30 was 3990cP. Don't go by the w rating itself until you look at all the actual viscs.

It's w-rating plus op visc to get a feel for the oil's visc. This is why AGAIN I say we need some good comparative visc graphs. Some visc curves cross twice!
 
We can't assume the composition of the oil will result in a straight line graph from 0 C to 100 C.
So it should be expected that oils will have variances in between.

BTW, I frequently start my car at 40C.
 
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