Why not dual sumps designs?

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May 3, 2022
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I know it seems weird but can't help thinking about it. What if car manufacturers decided to make a dual sump design. One for cold start oil and one for operating temperature oil.

This will allow us to fill monogrades that will eliminate the need for VIIs ,and thus, shearing altogether. And also would improve the cost of OCIs drastically.

Is there any reason why this idea might fail to stand a ground in real world?
 
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Oil mixing as it runs through the same engine even though at different times, cost to create and current multi grade oils getting engines to 200-300k reliably with good maintenance makes it just not worth integrating in to standard vehicles.
 
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If both oils are running through the same engine how do you keep them from mixing?

And besides why would you do this? Multi-viscosity oils are not anywhere the same as they were in the 80s. A lot of people come on here and pontificate about the supposed horrors of viscosity index improver polymers but if you’re buying a quality oil with an approval or a specification related to viscosity retention then it’s not a concern. Some of the oils on the market today are extremely viscosity stable. Most of the viscosity deviations we see in cheap UOA are due to fuel dilution not mechanical shear. What application do you have where you’ve got a verified problem with mechanical shear?
 
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I know it seems weird but can't help thinking about it. What if car manufacturers decided to make a dual sump design. One for cold start oil and one for operating temperature oil.

This will allow us to fill monogrades that will eliminate the need for VIIs ,and thus, shearing altogether. And also would improve the cost of OCIs drastically.

Is there any reason why this idea might fail to stand a ground in real world?
No possible because both sumps would share the same oil circuit. Bad idea because mongrades aren't the be all end-all. Needlessly complex, and would cost more toe maintain.
 
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If both oils are running through the same engine how do you keep them from mixing?
Once the engine was up to temp you have to pull over and wait for all the oil to drain back to the cold start sump, pull a lever to switch sumps, start up and go. Even then you're still going to end up with a Frankenbrew just from the residual oil left over from each switch over.
 

Astro14

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Even $10 Million Jet Engines use just one oil supply, though they have multiple scavenge pumps and a large sump.

One oil is all they need.

For everything from -65C up to 55C for engine start.
 
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I like the way you think, but this type of system would be unnecessarily complex for a normal passenger vehicle... owners have enough trouble not draining the transmission and then adding engine oil to the brake reservoir or radiator. And while the intentions are good, I really don't think this system would significantly extend the life of the engine. Modern multigrade oils are very good, just gotta stay on top of maintenance and try not to abuse your equipment.
 
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Very easy to solve that problem with single sump: variable oil pump between different temperature. You can based on oil temperature pump different amount of oil with computer adjusted flow metering.

I think that's what allows for 0w16 and even 0w8 oil these days.
 
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