Can 5W-30 flow at temperature X exactly like 0W-20 at temperature Y?
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I believe the graph uses degrees celsius. so 5 °C works out to 9°F
Yes.
That is called Viscosity Index and is widely variable depending on the base oils used and Viscosity Index Improver additive.
Yes. Especially in a Jeep with oil temps between 200f to 250f (off roading).
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Because every oil has a finite viscosity index, there is always some temperature difference that can make two oils have the same viscosity.
Define flow.
Yes, that's how all of this works. To make matters even more complicated, there are synthetic 15W and 20W-XX oils that pump more easily at -50ºF than some 5W-30 oils.
Even among 'high tech' oils, there are some lower viscosity AN based oils that won't pour or pump below about -30ºF and some PAO based higher viscosity oils that will pour at -44ºF or even lower.
Even among 'high tech' oils, there are some lower viscosity AN based oils that won't pour or pump below about -30ºF and some PAO based higher viscosity oils that will pour at -44ºF or even lower.
Speed of oil reaching the engine internals?
And part of that speed of reaching, " and maintaining " lube of the engine internals, is if the return flow provides enough oil back down into the sump pickup area to keep up with the demand intake of the oil pump. And even at the pickup, is the oil thin enough so the pickup does not end up creating a hole lacking oil around it, and end up sucking air.
Sometimes cold starting an engine in extremely cold temperatures ends up with that red oil light screaming at you for a while. The questions are, why, what is actually going on?
Yet the winter rating isn’t achieved. That’s because it’s about more than an oil pumping easier at very low temperatures. Exactly why the winter rating testing was changed in the late 80s.
Pumpability is really a binary. Either it will or it won’t. If it will pump it may require more energy to do so, but if it won’t, then that’s a bad situation.
To say that some 20W rated oil will pump easier at -50 is a good way to cause engine failure. The winter rating means something.
Also, as I know you’re aware, if an oil meets the requirements for a better winter rating then it must be labeled as such.
Flow is highly overrated on here, part of the misunderstanding of how oil systems work, compounded by a misunderstanding of what the winter rating means - and doesn’t mean.
Goofy and misleading YouTube videos don’t help for those that are inclined to believe such things.
So more energy is a good news because it means 10 unit of energy for making 0W-20 move at 2 feet/sec but 15 unit of energy to move 5W-30 at 2 feet/sec. It's like that, right? I would love that. As long as oil moves at 2 feet/sec who cares about energy. No?
Even if you did, odds are it’s just a pour test that is not relevant to engine, which has a positive displacement oil pump.
It’s a range. Not a tally. You ever hear of a 2.5 winter rating or 25 viscosity before? You’ll end up with pretty much an undetermined winter rating between 0/5 and either a higher range 20 or lower range 30.
Is it safe to use such a weird mixture?
Search @ZeeOSix ‘s informative posts about positive displacement oil pumps.
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