Do lower weight oils actually warm faster?

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Originally Posted By: Clevy
I don't think so. However they do get to optimal operating viscosity faster.


Clevy - I don't think I stated my question correctly - this is EXACTLY what I was wondering! It's common knowledge that it's easier for a motor running, for example, 5W-30 to turn over and successfully START than a motor running 10W-30, but you hit the nail on the head of my question, i.e., does a lower weight oil actually reach its optimal viscosity FASTER than a heavier weight oil???

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Ed
 
I think removing viscosity from the question may be the best way to look at it since you want it to be on-spec, just heat up faster.

Who cares if it heats up faster if it is then incorrect after fully coming up to temp for that engine.

PAO base stock has increased specific heat and thermal conductivity, so at the same viscosity it would store and spread heat more efficiently.

There are a few coolant boosts out there that may help. Amsoil tested theirs and found that from 30 to 180F took 35% less time. This solution would mean when up to temp you're then using the proper viscosity.
 
The thicker the oil, the faster it will be heated in bearings and the pump. However, if you are in by-pass mode, that does not mean that the sump oil will be heated faster. In addition, as the two oils warm they will become more and more similar in viscosity and the difference in heating due to internal friction will begin to go away. The heat from combustion will heat the two oils similarly. However, if you are in by-pass mode, the heating will not necessarily be making it to the sump at the same pace.

So yes, I think that thicker oil will warm faster at startup. However, I don't think that it will get to operating temperature much faster because the thick oil is rapidly reaching the viscosity of the thin oil as it gains heat.
 
Originally Posted By: GMorg
The thicker the oil, the faster it will be heated in bearings and the pump. However, if you are in by-pass mode, that does not mean that the sump oil will be heated faster. In addition, as the two oils warm they will become more and more similar in viscosity and the difference in heating due to internal friction will begin to go away. The heat from combustion will heat the two oils similarly. However, if you are in by-pass mode, the heating will not necessarily be making it to the sump at the same pace.

So yes, I think that thicker oil will warm faster at startup. However, I don't think that it will get to operating temperature much faster because the thick oil is rapidly reaching the viscosity of the thin oil as it gains heat.

Bypass is an internal feature of the filter, not an internal loop bypassing the sump. If a filter is in by-pass the fluid skips the filter. If it skipped the sump, you sprung a leak.

There is an over-pressure relief valve but that should not open at cold start unless you go immediately to redline on over-thick oil.
 
This whole business of comparing W rating numbers, without understanding them, is getting quite silly and reminds me of the plasma TV set contrast ratio wars. Various salespeople went all out (perhaps they still do, I just don't follow it) on the higher the number the better, while in reality human eye would never detect the difference once a certain threshold was reached. Of course no salesman was interested in presenting facts and most customers just went along with it.

The "W" rating is all about cold pumpability and not cold viscosity. The oil has to be pumpable at a certain temperature in order to get its W rating. The lower the temperature the lower the W rating number the oil can get, the viscosity of that oil can vary widely and it will in no shape affect the W rating.

Just look at some of the oils from Petro Canada below.
Look at the synthetic 0w20 and 0w30 oils. Both have 0W rating at -40C, but 0w20 is about 28% lighter at that temp.
Then look at the synthetic 5w30 and conventional 5w30, their CCV is pretty much identical at -35C, while in other grades there is a difference in CCV between synthetic and conventional.

Petro Canada Conventional Data Sheet

Petro Canada Synthetic Spec Sheet


What I'm trying to say is that:
1. The oil grades are just a guide. They do not mean much because they are meant to capture a range of viscosity at a given temperature. Just because an oil has a 0w in front of it, doesn't mean it will actually be thinner than another oil that has a 5w rating. In same cases it actually may be thicker.

2. As long as your operating temperature is below the cold cranking pumpubility for a particular W rating, the difference in viscosity will have absolutely no bearing on engine wear. All it means is that the thinner oil will be easier to crank. The positive displacement pump will ensure that the same amount of oil is delivered to the parts as long as it can pump the oil, that is the reason this type of oil pump is used.

The 5w rating is obtained at -35c, that is more than enough for the most situations out there. A 0w oil will be easier to start and that's it.
 
Originally Posted By: brandini
Originally Posted By: Nickdfresh
It's not a flawed question. I do use thinner oils (0W-30 M1 AFE) because I'm on the highway in 6 mins or so in some cold temps lately. But I once owned a beater 90' Buick LaSabre that took a very long time to heat up - but ran otherwise very well. I found running a 10W-30 conventional oil made a slight difference for heat in the winter as the engine had nearly 200K on it, though I suspect it might have had a thermostat issue...

Great flawed example as well.

It's not the temperature that you want, it's the flow. With the lower viscosity oil, you get to your goal earlier, but the headroom for high temperature could be lowered as well.


To me it doesn't matter, I do prefer flow over quicker heat. In this case it's a moot point since my car heats up relatively quickly on the highway, 0W-30 or 10W-30. But yeah, I think thinner is better generally speaking. The previous car I might not have been on the highway as much and it took forever to heat up in puttering around town. After 20-30 minutes, the oil will heat up to burn out condensation and fuel dilution even on the coldest days.
 
Originally Posted By: KrisZ
The "W" rating is all about cold pumpability and not cold viscosity. The oil has to be pumpable at a certain temperature in order to get its W rating.

Wrong, it takes a pass of two separate tests to earn a W rating at a given level.

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Just look at some of the oils from Petro Canada below.
Look at the synthetic 0w20 and 0w30 oils. Both have 0W rating at -40C, but 0w20 is about 28% lighter at that temp.

explained above.
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Then look at the synthetic 5w30 and conventional 5w30, their CCV is pretty much identical at -35C, while in other grades there is a difference in CCV between synthetic and conventional.

This observation only applies to these two oils, not all oil.

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What I'm trying to say is that:
1. The oil grades are just a guide. They do not mean much because they are meant to capture a range of viscosity at a given temperature. Just because an oil has a 0w in front of it, doesn't mean it will actually be thinner than another oil that has a 5w rating. In same cases it actually may be thicker.

It is possible for a manufacturer to label an oil passing the 0W test as 5W, but it would likely not be cost effective to do so. Again, the winter rating depends on a pass of 2 tests, not just one.

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2. As long as your operating temperature is below the cold cranking pumpAbility for a particular W rating, the difference in viscosity will have absolutely no bearing on engine wear. All it means is that the thinner oil will be easier to crank. The positive displacement pump will ensure that the same amount of oil is delivered to the parts as long as it can pump the oil, that is the reason this type of oil pump is used.

You can't make a qualified statement like this with "as long as" in it. This is exactly why the W rating is earned from 2 tests. Jello has way too high a viscosity for an engine, but it is still pumpable.
 
Originally Posted By: KrisZ
This whole business of comparing W rating numbers, without understanding them, is getting quite silly and reminds me of the plasma TV set contrast ratio wars. Various salespeople went all out (perhaps they still do, I just don't follow it) on the higher the number the better, while in reality human eye would never detect the difference once a certain threshold was reached. Of course no salesman was interested in presenting facts and most customers just went along with it.

The "W" rating is all about cold pumpability and not cold viscosity. The oil has to be pumpable at a certain temperature in order to get its W rating. The lower the temperature the lower the W rating number the oil can get, the viscosity of that oil can vary widely and it will in no shape affect the W rating.

Just look at some of the oils from Petro Canada below.
Look at the synthetic 0w20 and 0w30 oils. Both have 0W rating at -40C, but 0w20 is about 28% lighter at that temp.
Then look at the synthetic 5w30 and conventional 5w30, their CCV is pretty much identical at -35C, while in other grades there is a difference in CCV between synthetic and conventional.

Petro Canada Conventional Data Sheet

Petro Canada Synthetic Spec Sheet


What I'm trying to say is that:
1. The oil grades are just a guide. They do not mean much because they are meant to capture a range of viscosity at a given temperature. Just because an oil has a 0w in front of it, doesn't mean it will actually be thinner than another oil that has a 5w rating. In same cases it actually may be thicker.

2. As long as your operating temperature is below the cold cranking pumpubility for a particular W rating, the difference in viscosity will have absolutely no bearing on engine wear. All it means is that the thinner oil will be easier to crank. The positive displacement pump will ensure that the same amount of oil is delivered to the parts as long as it can pump the oil, that is the reason this type of oil pump is used.

The 5w rating is obtained at -35c, that is more than enough for the most situations out there. A 0w oil will be easier to start and that's it.


MRV for a 5W is measured at -35C, CCS for a 5W is measured at -30C. MRV for a 0W is measured at -40C, CCS for a 0W is measured at -35C. MRV and CCS roughly DOUBLE for every 5C step, so the 0W, compared to the 5W, you can halve its CCS/MRV figures to give you its viscosity at the same temps at the 5W.

Using the qualifier that we are speaking specifically of the temps that CCS and MRV are tested at, #1 is impossible based on what I just stated. A 5W cannot be thinner than a 0W at these temperatures, otherwise, it would be a 0W. Multigrade oils are required to be labelled with respect to the lowest W rating they can achieve.

Now, assuming you know that and are speaking of warmer start-up temps, you are somewhat correct. But the crossover point is much closer to 0 than many think it is for an oil like M1 0w-30 for example to start being heavier than your typical 5w-20.
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Now, because it is currently winter outside, if we are comparing 0w-xx and 5w-xx oils of the same grade, the 0w-xx oil is always going to be thinner on start-up at the temperatures Canada, and the Northern states are currently experiencing. Also, I would contest your wear point based on one fact and that is cylinder wall lubrication, which uses a spray of oil that comes from between the rod and crankshaft. With extremely viscous oil, this spray pattern is not as good, or as effective, as with an oil that is less viscous. And I'm speaking of cold, thick oil, not the difference between a 20w-50 and a 0w-20 at 100C. This is where using a 0w-xx MAY in fact give you a wear advantage during the winter months. How much it really makes a difference and what the contrast in wear rates would be though, I'm not sure. I don't have a handy dandy link to any sort of study on the matter
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Originally Posted By: brandini
It is possible for a manufacturer to label an oil passing the 0W test as 5W, but it would likely not be cost effective to do so. Again, the winter rating depends on a pass of 2 tests, not just one.


Nope, the labelling rules are that with the exception of monogrades with no VII, the oil MUST carry the lowest of the test that it meets.

Can't make a 0W, then sell it as a 5W,or 10W.
 
Originally Posted By: Shannow
Originally Posted By: brandini
It is possible for a manufacturer to label an oil passing the 0W test as 5W, but it would likely not be cost effective to do so. Again, the winter rating depends on a pass of 2 tests, not just one.


Nope, the labelling rules are that with the exception of monogrades with no VII, the oil MUST carry the lowest of the test that it meets.

Can't make a 0W, then sell it as a 5W,or 10W.

Well then he's even more wrong.
 
In response to brandini:

In addition to filter by-pass, there can be both pressure relief valves and pressure control valves (air-cooled VWs used both). In extreme cold, both of these valves can cause a "by-pass" mode that short-circuits oil back to the sump or the low pressure side of the pump.
 
True, but for the supposition of this topic, I'd assume we're talking about water-cooled vehicles running an oil that at start-up wouldn't cause over-pressure and zero lubrication. That's a separate problem to solve, and is usually addressed with warm-up time at high idle.
 
Originally Posted By: OVERKILL
Now, because it is currently winter outside, if we are comparing 0w-xx and 5w-xx oils of the same grade, the 0w-xx oil is always going to be thinner on start-up at the temperatures Canada, and the Northern states are currently experiencing. Also, I would contest your wear point based on one fact and that is cylinder wall lubrication, which uses a spray of oil that comes from between the rod and crankshaft. With extremely viscous oil, this spray pattern is not as good, or as effective, as with an oil that is less viscous. And I'm speaking of cold, thick oil, not the difference between a 20w-50 and a 0w-20 at 100C. This is where using a 0w-xx MAY in fact give you a wear advantage during the winter months. How much it really makes a difference and what the contrast in wear rates would be though, I'm not sure. I don't have a handy dandy link to any sort of study on the matter
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This "MAY" is what I'm contesting here, because while you in particular say "may", many are convinced that it in fact does significantly reduce wear. If extreme cold viscosity was so important to engine wear, the wide viscosity variation between grades would not be allowed. In other words, to get 0w rating, an oil would have to be pumpable at -40C AND have a certain viscosity instead of just having a maximum value, does not matter if its a 0w20, 0w30 or 0w40 oil. Yet, all these different grades of oil will have different viscosity at that temp. but still be pumpable.

My previous post was poorly written, my apologies.
We have many vehicles that can use 5w30 oil and were back specked to 5w20 oil. I often see recommendations to use a 0w20 or 0w30 oil in those cars. I was simply trying to illustrate that, in those situations, a 5w20 could actually be thinner when cold than a 0w30, if someone wanted a thinner oil. 0w20 would be the thinnest, of course, but I do not think many people realize this discrepancy in cold oil viscosity between oil grades.

The hot viscosity is pretty much the same between grades. A 30 grade will pretty much have the same hot viscosity in 0w, 5w or 10w ratings. The same cannot be said for the cold viscosity. That's what I was trying to illustrate. Again sorry for the very poor delivery.
 
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Originally Posted By: KrisZ

This "MAY" is what I'm contesting here. If extreme cold viscosity was so important to engine wear, the wide viscosity variation between grades would not be allowed. In other words, to get 0w rating, an oil would have to be pumpable at -40C AND have a certain viscosity instead of just having a maximum value, does not matter if its a 0w20, 0w30 or 0w40 oil. Yet, all these different grades of oil will have different viscosity at that temp. but still be pumpable.


Well it is viscosity that has the limit (that's why it is measured in cP). This is why CCS (which has a much more stringent visc cap than MRV) is important IMHO. The limit for a 0w-xx is 6,200cP @ -35C, so you have to be below that to get the 0w-xx rating. This doesn't matter if the hot visc is a 20 or a 40, it still has to have an adequately low (
Originally Posted By: KrisZ
My previous post was poorly written, my apologies.
We have many vehicles that can use 5w30 oil and were back specked to 5w20 oil. I often see recommendations to use a 0w20 or 0w30 oil in those cars. I was simply trying to illustrate that, in those situations, a 5w20 could actually be thinner when cold than a 0w30, if someone wanted a thinner oil. 0w20 would be the thinnest, of course, but I do not think many people realize this discrepancy in cold oil viscosity between oil grades.

The hot viscosity is pretty much the same between grades. A 30 grade will pretty much have the same hot viscosity in 0w, 5w or 10w ratings. The same cannot be said for the cold viscosity. That's what I was trying to illustrate. Again sorry for the very poor delivery.


For that to be the case, we would have to be quite close to 0C. We know the "doubling" or "halving" rule works up to around -15C FWIW.

So, let's take two oils: M1 AFE 0w-30 and PYB 5w-20 and extrapolate their viscosity backwards to that point. Both only give us MRV, so that's what we'll have to use

TEMP.....M1.......PYB
-40C.....13,250...---------
-35C......6,625...18,000
-30C......3,312....9,000
-25C......1,656....4,500
-20C........828....2,250
-15C........414....1,125

At some point, the 5w-20 will become thinner. @ 40C, the 5w-20 is 49.6cSt, the 0w-30 is 62.9cSt. So between -15C and 40C, that crossover happens. However, at the start-up temps that we've been experiencing lately, M1 AFE 0w-30 is obviously quite a bit thinner than PYB 5w-20.
 
Yes, M1 0W40 reaches operating temp couple miles sooner than Castrol 10W60, given the same ambient temp and driving condition in my M3. I'm talking about roughly 5 miles of freeway driving for M1 0W40, and 8 miles or so to heat up 10W60. Also, just my observation, the ambient temp could be 40F or 70F, it takes roughly the same driving distance on the freeway to reach operating temp.
 
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Originally Posted By: OVERKILL

TEMP.....M1.......PYB
-40C.....13,250...---------
-35C......6,625...18,000
-30C......3,312....9,000
-25C......1,656....4,500
-20C........828....2,250
-15C........414....1,125

At some point, the 5w-20 will become thinner. @ 40C, the 5w-20 is 49.6cSt, the 0w-30 is 62.9cSt. So between -15C and 40C, that crossover happens. However, at the start-up temps that we've been experiencing lately, M1 AFE 0w-30 is obviously quite a bit thinner than PYB 5w-20.


Lets substitute PYB for PP and at -35C we have M1:6,625 ....PP:9,000, the difference is much less.
Now lets substitute M1 to Shell 0w30 and at -35c we have Shell:9,450 ....PP:9,000.

Petro Canada's synthetic 5w20 (9,100) is also thinner at -35c than their 0w30 (11,450).

M1 ESP 0w30 is 26900 at -30C.

Like I said, it's not the same as the hot viscosity. Now why would it be like that? Why would the requirements only be for the maximum viscosity for the extreme cold spec, and be so specific as for the hot spec? Could it be that, as long as the oil is below the maximum, and is pumpable, there is little difference in wear protection during cold starts?

I ask again, if it was so important, why such a variation between 0w oils. Why would M1 0w20 be 9,200 at -40C , M1 AFE 0w30 be 13,250 and M1 ESP 0w30 be 26,900 at -30C or 107,600 at -40C? Those ar pretty big variation in viscosity for oils that have the same 0w rating.
 
Originally Posted By: KrisZ


Lets substitute PYB for PP and at -35C we have M1:6,625 ....PP:9,000, the difference is much less.


But it is still 3,000cP, and the relative difference persists right up until whatever the crossover is
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Originally Posted By: KrisZ
Now lets substitute M1 to Shell 0w30 and at -35c we have Shell:9,450 ....PP:9,000.


Yup, but you have to include CCS in your thinking about that as well, which we know for the 5w-20, was above the limit at -35C to classify it as a 0w-20. That's why it is nice to have both figures. I wish it was mandatory to include both on a PDS.

Also, you are comparing to a (much heavier) Euro 0w-30, which is like GC and wouldn't be cross-shopped here, that's why I chose the AFE 0w-30, as it is your typical PCMO style 0w-30. M1 0w-40 also has a relatively lacklustre MRV, but we know for CCS, it is under the limit at -35C.

However, you did bring up a great example with PP,as they actually list CCS for it. It is 4,000cP @ -30C. We know that the Shell 0w-30 is
Interesting the difference between the two tests eh? MRV tests pumpability, CCS is the Cold Cranking Simulator.

Originally Posted By: KrisZ
Petro Canada's synthetic 5w20 (9,100) is also thinner at -35c than their 0w30 (11,450).


Now THAT is a good find! As those are both PCMO's. So you DID manage to find an example, that is excellent, so I'll cede that one to you, victory sir! Did you notice their 0w-20 isn't much thinner either?

Originally Posted By: KrisZ
M1 ESP 0w30 is 26900 at -30C.


That's a typo. MRV has to be measured at the spec for the weight, so its MRV is 26,900 @ -40C, so 13,450 @ -35C, so a bit thinner than PYB but thicker than PP.

Originally Posted By: KrisZ
Like I said, it's not the same as the hot viscosity. Now why would it be like that? Why would the requirements only be for the maximum viscosity for the extreme cold spec, and be so specific as for the hot spec? Could it be that, as long as the oil is below the maximum, and is pumpable, there is little difference in wear protection during cold starts?


I don't think it is the wear, I think it is that it becomes unpumpable below that point, LOL! That's why I said earlier that the Cold Cranking viscosity (CCS) may be a better reference point, as the limit on it is much tighter.

Originally Posted By: KrisZ
I ask again, if it was so important, why such a variation between 0w oils. Why would M1 0w20 be 9,200 at -40C , M1 AFE 0w30 be 13,250 and M1 ESP 0w30 be 26,900 at -30C or 107,600 at -40C? Those ar pretty big variation in viscosity for oils that have the same 0w rating.


Well the limit is 60,000cP for MRV, so we know that last one is wrong, LOL! But for CCS, they all have to be under the limit of 6,200cP, which is a lot more stringent and they will be all a lot closer to that limit than they are to the MRV.

I think the "importance" thing is relative
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but I know that I'd rather have the AFE 0w-30 in the sump (or the 0w-20, which I do have) than the others due to what I mentioned about cylinder lubrication earlier. Another good choice would be the EP 0w-20.

I don't think about it in terms of comparing it to hot viscosity, just about how much less it thickens as the temperature plummets; about keeping the oil as thin as I can as the temperature goes down. This allows better cold cranking and better splash lube in places that receive it. And better spray lube in areas that see that. This also, IMHO, means that there is less time on the pressure relief and less time on bypass, though that may be completely irrelevant in the big scheme of things, I just figured I'd mention it. My biggest "hangup" here is cylinder spray lube, which I think is a genuine thing to think about, as it is something that once an oil does get down to these extremely low temperatures and high viscosities, that may actually be affected
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That's my theory anyway, LOL!
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