Can someone give me a website to help explain oil and how it thins out etc

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Originally Posted by NattyBoh
Originally Posted by ZeeOSix
Originally Posted by NattyBoh
Then he was saying well it thicker cold and thinner hot ...


Yes, basically every liquid on earth gets thinner as it heats up.

The oil viscosity rating numbers are at two different temperatures. There is no connection between the first "W" (cold rating) and the last number (hot rating).


Ahh. I know it gets thinner as it heats up but then.... whatever lol Im confused on how it goes from a 5 weight to a 40 weight. Or it doesnt? Then why use a 5w40 for cold temps , to improve/help cold starts right? Because the film strength/weight is lower when cold?


In a simple nutshell.

5W-30 is thinner at cold temps than 10W-30. The "W" number is lower.

5W-30 and 10W-30 are essentially the same viscosity at hot 212 F (100C) temperature. The 2nd numbers are the same.

5W-30 is thinner than 5W-40 at hot 212 F temperature. The second number is lower, so it's thinner at 212 F.

You have to compare the first to the first number, and compare the 2nd to the 2nd number. The lower the number, the thinner the oil under the same conditions.
 
Viscosity index Improve help oil resist thinning when hot.
5w rating is for extreme cold weather pumpability. Or for example the CCV cold crank viscosity.
At -30c the 5w can have a viscosity up to 6600 cst

The second number 40 indicates the oil viscosity rating(not number it's a range) at 100 c.
So for example the oil has a 100c viscosity of 13 centisteokes, that's a 40 weight.


So 6600 is much thicker than 13 for example. A higher viscosity index base oil will have the oil be thinner at cold temperatures while maintaining the desired hot viscosity,
 
Originally Posted by NattyBoh
Originally Posted by ZeeOSix
Originally Posted by NattyBoh
Then he was saying well it thicker cold and thinner hot ...


Yes, basically every liquid on earth gets thinner as it heats up.

The oil viscosity rating numbers are at two different temperatures. There is no connection between the first "W" (cold rating) and the last number (hot rating).


Ahh. I know it gets thinner as it heats up but then.... whatever lol Im confused on how it goes from a 5 weight to a 40 weight. Or it doesnt? Then why use a 5w40 for cold temps , to improve/help cold starts right? Because the film strength/weight is lower when cold?

5W represents the ability to flow/pump at a ridiculously cold temperature. Temperature that will kill humans quickly if that's the ambient temp. 30 represents a biscottis range at the boiling point of water. Everything in between is up for grabs, although there is obviously interpolation of what happens in between when something like 10W-30 is only recommended at a higher ambient temperature than 5W-30. Possibly also assumptions made about the high temperature stability.

I use a 0W-40 that's thicker at startup than most 5W-30 at spring to fall temperatures.
 
Originally Posted by MasterSolenoid
From my internet reading, and I may be wrong, but

I always thought one of the additives they put into (multi-viscosity) oil was like small coil springs (for lack of correct word).
When these coil springs get hotter, they start stretching out which thickens the oil.
When oil gets used, it shears (lower viscosity), because these coil springs are getting chopped-up in your engine (cams, timing chain).

Edit: 5w-40 would start out as 5 and thicken to 40 once engine is at operating temperature.

The gist is correct that VI improvers are long chains that expand at higher temperatures, which then keeps viscosity higher than if it wasn't there. However, 5W is at a ridiculously low temp. 5W needs to pump at -30 deg C. A lot of things can happen between -30 deg C and 100 deg C.
 
Originally Posted by NattyBoh
Ahh. I know it gets thinner as it heats up but then.... whatever lol Im confused on how it goes from a 5 weight to a 40 weight. Or it doesnt? Then why use a 5w40 for cold temps , to improve/help cold starts right? Because the film strength/weight is lower when cold?

Again it does not go from a "5 weight" to a "40 weight". You continue to conflate the two numbers, the one with the "W" is better thought of as a performance rating and the one after the dash (in this case 40) as the operating viscosity. There is no SAE 5 oil.

An oil that meets the performance specifications for a 5W is labeled as such and can be anything between a 20 grade and a 50 grade at operating temperature. For the purposes of this discussion they are not linked together, one is a cold weather spec and like I mentioned would probably be better represented as something other than a number.

5W-40 is not a "5 weight" when cold. Yes it is a "5W" but that is not the same "5" as the grade at operating temperature. They are two very different measurements.
 
I think I found the right chart. This one shows a hypothetical set that includes a SAE 10, SAE 30, and a 10W-30. There's still some wiggle room where they don't have to meet at the precise temps but they will eventually meet. Now there might be some other details, such as the inherent viscosity index of certain base oils or blends of base oils. I understand that one of the advantages of PAO and esters being blended was that it actually increased the overall VI. I thought I heard somewhere that Mobil 1 10W-30 from the 90s didn't have any VI improver at all.

https://www.machinerylubrication.com/Read/1327/viscosity-index-improvers

[Linked Image]


Of course this doesn't necessarily hold the same for every conceivable motor oil of the same weight on the label. A "straight weight" motor oil by definition doesn't have any VI improver, but it could still have a relatively high VI. I've heard that modern SAE 30 oils made with Group II base oils might even be considered 15W-30 or 20W-30. There could be straight weight synthetic oils if they really wanted to label them. I thought that Red Line said their 30 wt race oil is technically a 10W-30.
 
I think people who don't know anything about oil get confused because they hear the word ‘weight' and think that the W means that. I honestly don't know what the word weight has to do with engine oil or why folks use that term. I thought oil came in grades.
 
Originally Posted by CT8
I wouldn't worry about it.

But that is what propels this entire website. Technical worry of minutia, things you can't change and the feeling of being right. You could read the owner's manual but that's not nearly as much fun!
 
Originally Posted by Piston_slap
Originally Posted by CT8
I wouldn't worry about it.

But that is what propels this entire website. Technical worry of minutia, things you can't change and the feeling of being right. You could read the owner's manual but that's not nearly as much fun!




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Originally Posted by Patman
Originally Posted by Piston_slap
Originally Posted by CT8
I wouldn't worry about it.

But that is what propels this entire website. Technical worry of minutia, things you can't change and the feeling of being right. You could read the owner's manual but that's not nearly as much fun!




01.gif


You get to the point where the minutia doesn't make enough difference to matter , yet the because some one read a marketing story about what ever with out knowing what they are reading about think the read information is fact. For Example the old 101 series many thought the article was factual and regurgitated the writing as gospel and not only on BITOG but on many other sites. I rebuilt a 455 Pontiac motor for a friend and at start up he looked at the oil pressure gauge and said WOW the oil pressure at 2000 rpm was 40 psi it's too high ! This was a 15w - 40 oil and the engine was just started! He went through the we need to get a thinner oil and the whole oil 101 regurgitation that he read on Ferrari chat.
 
Originally Posted by Sonic
I think people who don't know anything about oil get confused because they hear the word ‘weight' and think that the W means that. I honestly don't know what the word weight has to do with engine oil or why folks use that term. I thought oil came in grades.

The SAE engine oil viscosity ranges were all based on contemporary technology. It hasn't really scaled all that well with newer technology such as VI improver and high VI oil. I agree with other sentiments that it would be better if the current system no longer continued. There really is no relation between these arbitrary viscosity ranges and modern requirements. It was always a kludge.
 
Originally Posted by CT8

You get to the point where the minutia doesn't make enough difference to matter



So why are you even on here anymore? Seriously, why? All you ever seem to post is that no matter what oil you choose and no matter what oil filter you run, it doesn't matter. So then go away and let us have meaningful technical discussions about oil, because some of us are genuinely interested in the facts, but you clearly just want to make ridiculous and useless comments all the time that serve no purpose on this forum. You sound like a grumpy old man.
 
Originally Posted by Patman
Originally Posted by CT8

You get to the point where the minutia doesn't make enough difference to matter



So why are you even on here anymore? Seriously, why? All you ever seem to post is that no matter what oil you choose and no matter what oil filter you run, it doesn't matter. So then go away and let us have meaningful technical discussions about oil, because some of us are genuinely interested in the facts, but you clearly just want to make ridiculous and useless comments all the time that serve no purpose on this forum. You sound like a grumpy old man.

In many ways our discussions here are more about the proverbial angels dancing on the head of a pin. As a practical matter (save outliers where there was a defect) following the manufacturer's recommendation is all that's needed for engine longevity.

It's certainly fun hearing about other countries where the same carmaker has different recommendations. And discussion about well known failures in specifications.
 
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