Why do some people say 0W20 can cause more leaks compared to a 5W20?

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53
Sorry if this has already been discussed but my car is spec'd for 5w20 but here in Canada we get horrible winters as cold as -40 fahrenheit some days so a 0W20 obvs wouldn't hurt. I was doing some reading and seems like I read some posts about some people say "if you run 0W20, watch out for leaks"
I just dont understand how thats possible unless I am misinformed. A 0W oil will be less viscous compared to a 5W oil at a cold temperature, whatever the benchmark cold temp is. And then the second number is at operating temp and at this case they are the same.

For example, lets say its cold out. then a 5w20 would be viscous and as the temps heat up in the engine, it would slowly heat up and become less viscous until it reaches that 20 grade. However when a 5W20 is heating up, it would obviously be less viscous compared to a 0W20 that is cold right? In that case, If a 0W20 was said to cause leaks then in this same scenario wouldn't the 5w20 cause that same leak when it is warming up/engine is getting to operating temp? or am i missing something here


thanks!
 
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10
Location
Dallas, TX
Oil thickens as it heats up. 0 weight (0w20 when cold) is thinner than 5 weight (5w20 when cold) and is more likely to leak. At operating temperature a 0w20 and 5w20 are both 20 weight and are therefore the same thickness and equally likely to leak.
 
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Kendall, FL
Syntheyic vs Synthetic

I've not heard of this. The difference between them is often 1or 2 [email protected] 40°c, with some 0W actually being slightly more viscous. And at temps where these two grades actually start to have significant divergence (-30° and lower), they are much more viscous than their respective 40° cSt.
 
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5,128
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down in the park
Oil thickens as it heats up. 0 weight (0w20 when cold) is thinner than 5 weight (5w20 when cold) and is more likely to leak. At operating temperature a 0w20 and 5w20 are both 20 weight and are therefore the same thickness and equally likely to leak.

Oil thins as it heats up. There's no appreciable difference in oil viscosity between a 0W20 and 5W20 anywhere in the range, unless you approach the lower temperature limit of 5w20 where the viscosity will rise quickly.
 
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16,531
Location
Upper Midwest
Oil thickens as it heats up. 0 weight (0w20 when cold) is thinner than 5 weight (5w20 when cold) and is more likely to leak. At operating temperature a 0w20 and 5w20 are both 20 weight and are therefore the same thickness and equally likely to leak.
What on earth are you talking about? Oil does not thicken as it heats up, that would defy the laws of physics.

And as noted unless it is extremely cold the oil with the 5W winter rating is not necessarily thinner than the one with the 0W rating. And even if it is both are very thick at lower temperatures.
 

4WD

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15,778
Location
Texas
Oil thickens as it heats up. 0 weight (0w20 when cold) is thinner than 5 weight (5w20 when cold) and is more likely to leak. At operating temperature a 0w20 and 5w20 are both 20 weight and are therefore the same thickness and equally likely to leak.
Oil might thicken when it has too many miles on it in non DI … not much else will have that effect …
 
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1,794
Location
Danville, Indiana
Oil thickens as it heats up. 0 weight (0w20 when cold) is thinner than 5 weight (5w20 when cold) and is more likely to leak. At operating temperature a 0w20 and 5w20 are both 20 weight and are therefore the same thickness and equally likely to leak.

Wait a minute. What? How is that? For example, Mobil 1 AFE 0w20 is around 45 mm2/s at 40 degrees C but is only 8.8 at 100 degrees. Unless I'm bass ackward, or don't understand the measurement, that oil is about 5x thinner when at operating temp than it is when at 40.
 
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Messages
10
Location
Dallas, TX
Oil thickens as it heats up. 0 weight (0w20 when cold) is thinner than 5 weight (5w20 when cold) and is more likely to leak. At operating temperature a 0w20 and 5w20 are both 20 weight and are therefore the same thickness and equally likely to leak.
What on earth are you talking about? Oil does not thicken as it heats up, that would defy the laws of physics.

And as noted unless it is extremely cold the oil with the 5W winter rating is not necessarily thinner than the one with the 0W rating. And even if it is both are very thick at lower temperatures.
I'm glad this question was posted because this is a concept I was totally confused on.
 
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1,967
Location
USA
In that case, If a 0W20 was said to cause leaks then in this same scenario wouldn't the 5w20 cause that same leak when it is warming up/engine is getting to operating temp? or am i missing something here

Based on your words- you may be missing a critical point which could be the premise of your entire concern.

Oil does NOT "cause" a leak in any case ( except in the rare case of a chemical compatibility with a sealing material)

By definition, a "leak" is a passage between mating surfaces ( any number of sizes, configurations and restrictions)

Changes in viscosity ( resistance to movement) can have an effect on how much liquid can move along the leak path in a given state to a lower pressure environment depending on other influences such as pressure, gravity, temperature, capillary forces and so forth but they are not the "only" or even the "deciding" factor in that equation.
 
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335
Location
Florida
Based on your words- you may be missing a critical point which could be the premise of your entire concern.

Oil does NOT "cause" a leak in any case ( except in the rare case of a chemical compatibility with a sealing material)

By definition, a "leak" is a passage between mating surfaces ( any number of sizes, configurations and restrictions)

Changes in viscosity ( resistance to movement) can have an effect on how much liquid can move along the leak path in a given state to a lower pressure environment depending on other influences such as pressure, gravity, temperature, capillary forces and so forth but they are not the "only" or even the "deciding" factor in that equation.
Best definition of "leak". I'm tired of people saying oil cause leaks. Oil might show it, it might reveal it, but in the vast majority of cases, it doesn't cause it. Causation vs correlation is something that should be taught in school, starting in 5th grade. But that ain't not never gonna happen.
 
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