A Japanese scientist just put a number on the thickest any fluid can theoretically get: 10 to the 30th power pascal-seconds. That’s a one followed by 30 zeros. For reference, the motor oil sloshing around your engine block sits somewhere around a thousandth of a single pascal-second.
Honey clocks in at about 10. Professor Masaki Yoshida at Ritsumeikan University published his findings last month in the journal Physics of Fluids, and the number is so large it describes a material that doesn’t move at all. Any measurable flow would take longer than the Earth has existed.
In practical terms, you’re talking about something rigid. A rock, not a lubricant. Yoshida wasn’t chasing a better motor oil formula — he was chasing the boundary of physics itself.
The study drew on decades of geodetic data, along with laboratory rock-deformation experiments and simulations modeling geological processes that play out over millions of years beneath the crust. The materials exhibiting the highest viscosity aren’t anything you’d pour from a bottle. They’re the mineral building blocks of tectonic plates, flowing under unimaginable heat and pressure at speeds that make glaciers look like sprinters.
For fluid-dynamics researchers, the finding replaces a lazy but longstanding convention. Scientists have traditionally plugged “infinite viscosity” into their models when dealing with the upper extreme. Yoshida’s number gives them an actual ceiling, plus or minus two orders of magnitude.
It’s so astronomically high that it won’t change the math for anyone studying conventional fluids. That’s precisely why nobody bothered nailing it down until now.
But there’s a thread connecting this esoteric geology research to every car on the road. Viscosity is viscosity. The same physical property that determines whether your 5W-30 can protect cylinder walls at startup in January also governs how magma creeps through the Earth’s mantle.
The scale is absurdly different. The physics are not.
Ritsumeikan University suggests the findings could prove useful in studying geologic activity and high-viscosity non-Newtonian fluids — materials like ketchup whose viscosity changes under force. Shake the bottle and it flows. Leave it alone and it sits there mocking you. These substances occupy a gray zone between solid and liquid behavior that engineers across industries, automotive included, deal with constantly.
The motor oil world operates in a narrow, carefully engineered band of viscosity. Multi-weight oils are formulated to behave like a thin fluid when cold and a thicker one when hot, measured at multiple temperatures and indexed into the familiar numbers stamped on every bottle. The gap between a 0W-20 synthetic and the theoretical cosmic maximum is roughly 33 orders of magnitude.
That’s not a gap. That’s a chasm so vast it’s almost meaningless.
Almost. Because knowing where the wall is — even if it’s impossibly far away — is how science works. You map the boundaries, then you understand everything inside them a little better. Yoshida didn’t build a better engine oil, but he told us exactly how far the concept of “fluid” can stretch before the word stops meaning anything at all.
Your engine doesn’t care about tectonic viscosity. But the physics holding your crankshaft together and the physics holding continents together answer to the same rules. One just takes a lot longer to notice.
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