Help me understand winter ratings

BigShug681 said:
When would an oil become unable to be pumped? For instance would a 15W-xx have this happen under -13 F or would this be a much lower temp such as an oils pour point
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When the oil will not flow to the pickup tube under low pressure shear. This is specifically part of why the winter rating is a better indicator of cold-weather performance than the pour point.
 
kschachn said:
When the oil will not flow to the pickup tube under low pressure shear. This is specifically part of why the winter rating is a better indicator of cold-weather performance than the pour point.
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Ok so under the 15wxx at -13 F you would start running into these issues with oil not being able to be pumped, does anyone have a chart showing winter ratings and their temp rating?
 
OVERKILL said:
Under the SAE rules, an oil must be labelled with the lowest Winter rating it meets. The only exception applies to monogrades (no VII's), which can be labelled as either their 100C grade, or also carry a Winter rating.

While that's absolutely true when discussing different grades, and heck, sometimes not even different grades, a 0W-30 with a VI of 161 is going to be heavier than a 5W-30 than a VI of 190 at any point below 100C (assuming they have the same 100C visc) until some point below 0C, it's really immaterial because as long as the Winter rating is appropriate for the ambient conditions, you'll be fine.

However, it should be noted that oils ARE allowed to slip a Winter rating in service, so if you are close to the limit, it's quite possible to be out of spec after the oil has some miles on it. I've told the story of starting our Expedition with 5W-30 Pennzoil Ultra in the pan when it was -30C in Quebec and it barely rolled over, I didn't think it was going to start. The same temp with M1 0W-30, and it started just fine.
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Just going to add a graphic to this from Infineum:
Screen Shot 2022-08-07 at 12.06.09 PM.jpg
 
BigShug681 said:
Ok so under the 15wxx at -13 F you would start running into these issues with oil not being able to be pumped, does anyone have a chart showing winter ratings and their temp rating?
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Overkill posted a chart showing at what temperatures the oil must pass the test.
 
Everyone talks about and oil pumpability based on winter rating which factual, butdoes this take into account the head losses of the oiling system?

For example some engines have a crank mounted oil pump and may have up to two feet of pickup tubing from the pickup screen to the oil pump, so although the oil pump may pump the liquid, it may be too thick for the pump to create adequate suction and can cause air pockets. Once it gets to the pump the pump can certainly pump it at its intended rating but I do not think the winter ratings were designed for or tested for suction of a pump.

Maybe I wrong.
 
Drew7a said:
For example some engines have a crank mounted oil pump and may have up to two feet of pickup tubing from the pickup screen to the oil pump, so although the oil pump may pump the liquid, it may be too thick for the pump to create adequate suction and can cause air pockets. Once it gets to the pump the pump can certainly pump it at its intended rating but I do not think the winter ratings were designed for or tested for suction of a pump.

Maybe I wrong.
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“Suction” at the pump pickup is exactly one of the things the winter rating represents.
 
This started June and didn't make any valve noise. 5w-30 Penz platinum. I run wally world ST synthetic 10w-30 in my wife's car and it starred that morning as well. Both vehicles stay outside and don't have engine heaters.
20220127_070654.jpg
 
kschachn said:
“Suction” at the pump pickup is exactly one of the things the winter rating represents.
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So you are saying the winter ratings test for all sizes and lengths of the pickup tubes and no matter the length or size of the tube and you met the temperature rating the pump will provide enough "suction"?

I did not know that these tests covered all these different variables. I thought the test was run a specific apparatus.
 
Drew7a said:
So you are saying the winter ratings test for all sizes and lengths of the pickup tubes and no matter the length or size of the tube and you met the temperature rating the pump will provide enough "suction"?

I did not know that these tests covered all these different variables. I thought the test was run a specific apparatus.
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The test was originally setup to simulate the pump draw from the Jeep 4.0L engine, which had an insanely long pick-up tube, and was supposed to be the "worst case" scenario. This limited the MRV to 45,000cP. However, that was later deemed obsolete and the figure bumped to 60,000cP to represent more modern engines.
 
Drew7a said:
So you are saying the winter ratings test for all sizes and lengths of the pickup tubes and no matter the length or size of the tube and you met the temperature rating the pump will provide enough "suction"?

I did not know that these tests covered all these different variables. I thought the test was run a specific apparatus.
Click to expand...
It’s not the comparatively small diameter pickup tube or its length that is really the problem. The potential problem is in the area around the pickup screen. If it makes it into the tube then it will make it the rest of way. Using the “suction” analogy, the pump can pump the oil that’s in the tube and in the immediate vicinity of the screen. But the shear in the outlying oil causes it to create a void which then causes cavitation.
 
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