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I always use the recommended Mobil 0W-40 synthetic oil in my SRT.

I found an interesting study of the advantages of using thinner weight oil. Here is what was said:


Thinner oil flows quicker at cold start-up to begin lubricating critical engine components much more quickly than thicker oil can. Most engine wear takes place during cold start-up before oil flow can reach all the components. So, quicker flowing thinner oil will help reduce start-up engine wear, which is actually reducing wear overall.
  • The more free flowing thinner oil at cold start-up, is also much less likely to cause the oil filter bypass to open up, compared to thicker oil. Of course if the bypass opened up, that would allow unfiltered oil to be pumped through the engine. The colder the ambient temperature, and the more rpm used when the engine is cold, the more important this becomes.
  • Thinner oil also flows more at normal operating temperatures. And oil FLOW is lubrication, but oil pressure is NOT lubrication. Oil pressure is only a measurement of resistance to flow. Running thicker oil just to up the oil pressure is the wrong thing to do, because that only reduces oil flow/lubrication. Oil pressure in and of itself, is NOT what we are after.
  • The more free flowing thinner oil will also drain back to the oil pan quicker than thicker oil. So, thinner oil can help maintain a higher oil level in the oil pan during operation, which keeps the oil pump pickup from possibly sucking air during braking and cornering.
 

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I always use the recommended Mobil 0W-40 synthetic oil in my SRT.

I found an interesting study of the advantages of using thinner weight oil. Here is what was said:


Thinner oil flows quicker at cold start-up to begin lubricating critical engine components much more quickly than thicker oil can. Most engine wear takes place during cold start-up before oil flow can reach all the components. So, quicker flowing thinner oil will help reduce start-up engine wear, which is actually reducing wear overall.
  • The more free flowing thinner oil at cold start-up, is also much less likely to cause the oil filter bypass to open up, compared to thicker oil. Of course if the bypass opened up, that would allow unfiltered oil to be pumped through the engine. The colder the ambient temperature, and the more rpm used when the engine is cold, the more important this becomes.
  • Thinner oil also flows more at normal operating temperatures. And oil FLOW is lubrication, but oil pressure is NOT lubrication. Oil pressure is only a measurement of resistance to flow. Running thicker oil just to up the oil pressure is the wrong thing to do, because that only reduces oil flow/lubrication. Oil pressure in and of itself, is NOT what we are after.
  • The more free flowing thinner oil will also drain back to the oil pan quicker than thicker oil. So, thinner oil can help maintain a higher oil level in the oil pan during operation, which keeps the oil pump pickup from possibly sucking air during braking and cornering.
*nice write up!!

Has engine wear increases over time so should engine oil weight... True Fact!!!!
 

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That makes sense. And makes me feel better about running the OEM suggested 5-20 in my R/T.
 

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I always use the recommended Mobil 0W-40 synthetic oil in my SRT.

I found an interesting study of the advantages of using thinner weight oil. Here is what was said:


Thinner oil flows quicker at cold start-up to begin lubricating critical engine components much more quickly than thicker oil can. Most engine wear takes place during cold start-up before oil flow can reach all the components. So, quicker flowing thinner oil will help reduce start-up engine wear, which is actually reducing wear overall.
  • The more free flowing thinner oil at cold start-up, is also much less likely to cause the oil filter bypass to open up, compared to thicker oil. Of course if the bypass opened up, that would allow unfiltered oil to be pumped through the engine. The colder the ambient temperature, and the more rpm used when the engine is cold, the more important this becomes.
  • Thinner oil also flows more at normal operating temperatures. And oil FLOW is lubrication, but oil pressure is NOT lubrication. Oil pressure is only a measurement of resistance to flow. Running thicker oil just to up the oil pressure is the wrong thing to do, because that only reduces oil flow/lubrication. Oil pressure in and of itself, is NOT what we are after.
  • The more free flowing thinner oil will also drain back to the oil pan quicker than thicker oil. So, thinner oil can help maintain a higher oil level in the oil pan during operation, which keeps the oil pump pickup from possibly sucking air during braking and cornering.
Maybe olive oil would be better for all cars no matter what engine your running. Its a lot thinner and so would flow like hell.
 

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Summer time hot weather climates- weight of my oil goes up no cold starts. lol

As engine wear increases, weight of oil goes up. lol No doubt!!!
 

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Ha... thought I'd resurrect this old thread just for fun :)

I always thought that 0W-40 was actually 40 weight oil fortified to act like 0 weight when it gets cold. However, I was wrong.

It's actually 0 weight oil fortified to act like 40 weight when it gets hot. May not sound like much of a difference, but if ya think about it, it makes sense. Good to know what you're running.

That's part of the reason when 0W-40 gets old and tired, it can't "act" like 40 weight any more. The VII molecules that make it "act" thicker when it gets hot... wear out over time.

The way VI Improvers (VII's) work is that the huge molecules tend to coil up into balls when cold, thus having limited effect on the oil’s flow (viscosity). When hot, however, the molecules uncoil and stretch out, thus causing an increase in viscosity. The thin oil ACTS thicker when it gets hot.
 

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*nice write up!!

Has engine wear increases over time so should engine oil weight... True Fact!!!!

Only if oil pressure drops below some acceptable threshold. Maybe.



Really though if the engine has suffered enough wear -- mostly in the main/rod bearings areas -- to cause a fall in oil pressure heavier oil isn't the answer. An engine refresh is the answer.


BTW, I put 317K miles on a car and its engine and the engine was just as happy with 0w-40 oil at 300K+ miles as it was at 0K miles. Another car I ran it up to 161K miles and hot oil pressure was unchanged from when I bought the car -- used -- with <10K miles on it to when it has 161K miles on it. A number of other cars I put close to 150K miles on the engine and never had to deviate from the factory recommended oil. The engines never developed/manifested any indication the oil recommended by the factory was in any way insufficient to the task.


Oil consumption remained nearly constant as well.



There is really minimal wear with proper oil selection and servicing. The offering of "high mileage" oils by oil companies is just marketing.
 

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I read that also and it make sense.

Let me ask this question. True, 0 will flow faster, better, at cold start.

I also read (somewhere) that 0 does not offer the same "protection" as 5.

(3.6 V6 uses 5-20.)

So faster flow is better protection, but the oil at that time, before it's fully heated up, may not be thick enough to protect.

That's a good point too.

What do you guys think?
 

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I read that also and it make sense.

Let me ask this question. True, 0 will flow faster, better, at cold start.

I also read (somewhere) that 0 does not offer the same "protection" as 5.

(3.6 V6 uses 5-20.)

So faster flow is better protection, but the oil at that time, before it's fully heated up, may not be thick enough to protect.

That's a good point too.

What do you guys think?
Its the other number at the end, where it flows like 0W when cold, but when hot it protects like 40W.

The OW-40 spec covers a wide ambient operating range that would be in North America from the colder environments to the hotter ones.
 

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Correct. My post was on that time for the engine (oil) to warm up. I don't know the exact details, but let's say it takes 10 seconds for the oil to get hot. From 1 second to 9 second, would the 0 oil offer you less protection than 5, even if it flows faster?
 

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I read that also and it make sense.

Let me ask this question. True, 0 will flow faster, better, at cold start.

I also read (somewhere) that 0 does not offer the same "protection" as 5.

(3.6 V6 uses 5-20.)

So faster flow is better protection, but the oil at that time, before it's fully heated up, may not be thick enough to protect.

That's a good point too.

What do you guys think?

Modern synthetic oils are marvelous oils. They flow very well at cold temperatures. It was the problems the US military was running into when operating in cold climate theaters that started the work on synthetic oil, at least on the USA side. On the Axis side it was Germany trying to come up with suitable lubricating oil absent having access to enough crude oil. (Romania was the primary supplier of aviation fuel, gasoline, oils, greases to Germany and it is a long way -- approx. 1500km -- from Romania to Germany and this route was open to allied bombing/strafing at least in the later stages of the war. Trains pulling tanker cars full of gasoline, diesel, and lubricating oils make for nice bomb/strafing targets. So too did the refineries located in Romanian oil fields, albeit these had pretty good anti-air craft gun emplacements.)



Modern synthetic oils also have a good high temperature viscosity index. They do not need VII (viscosity index improvers) which are quite common with mineral oils. In the case of mineral oil VIIs are used which when cold unwind which tend to make the oil flow better cold. And there are VIIs that the other end which curl up when hot to make the oil "thicker". These VIIs can and do break down and they become less effective over the miles.



The '0' in 0w-40 (for example) is the low temperature (32F) viscosity index. It really has no bearing (no pun...) on how the oil performs at high temperature. That is the what the "40" is for. This is the high temperature (212F) viscosity index.


Thus a 0w-40 oil will flow like a 0w oil cold and yet offer high temperature high stress protection of a 40 weight oil when hot (and everywhere in between).



'course, not every engine is spec'd to use a 0w-40 oil. While my Hellcat is my Mini JCW engine requires 0w-20 oil.


Generally speaking a 0w-XX oil is better than a 5w-XX oil due to it better cold flow -- and at least one automaker says to use 0w-40 oil in temperatures -25C or colder -- but always use the viscosity grade of oil recommended by the automaker. There are other considerations -- variable cam timing, variable valve lift, MDS, etc. -- that also affect viscosity selection.
 

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Correct. My post was on that time for the engine (oil) to warm up. I don't know the exact details, but let's say it takes 10 seconds for the oil to get hot. From 1 second to 9 second, would the 0 oil offer you less protection than 5, even if it flows faster?
Great question. Yes, "0" weight offers less protection than higher weights. But this is not the question. Reason being is that "0" weight offers BETTER protection than no oil at all. This is the issue. Certain areas of the engine have no oil at start up. Straight 40 weight oil is like pancake batter at 0 degrees F.

Engine oil warm up: the big question is, how long does it take oil to begin flowing to critical parts when it's first started? Engine heat translates to a rise in oil temperature and thus improvement in oil flow, but this takes time, and much more than 10 seconds. But the majority of engine wear takes place right at start up. Those first few seconds are critical because no oil reaches critical areas. Whether it's one second or 10, the truth remains: thick oil flows slower than thin oil. This means that it takes longer to reach critical areas at start up. This is the purpose for having super thin (O weight) oil. At start up, it reaches critical wear areas quicker.

However, at operating temps, ya don't want this super thin oil. That's why the 0W40. Our super thin oil acts like much thicker oil at higher temps. Wouldn't it be great if we could have magic oil? I'm reminded that engineers have created magnetic fluid that changes viscosity in high end shocks and struts. Imagine having something like this in engine oil: oil that's able to instantly change viscosity like magnetic ride shocks do...

:)
 

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...Modern synthetic oils ... do not need VII (viscosity index improvers) which are quite common with mineral oils. In the case of mineral oil VIIs are used which when cold unwind which tend to make the oil flow better cold. And there are VIIs that the other end which curl up when hot to make the oil "thicker".
Was thinking about what you wrote here. I've only copied the quotes I'd like to address. I hesitate to say this, as like any one of us, I can be wrong, and also because I have a lot of respect for what you've written, both here and in the past.

That said, VII's are mandatory for multi-grade mineral oils. They cannot achieve for example a 10W30 rating with out it.
Though synthetic oils naturally flow much better at cold temps than regular oil, VII's are put in many of them as well, especially those that have a huge difference between their cold and hot numbers. Difference is, they naturally flow better at cold temps and don't require near as much VII intervention. VII's are used in both types of oils, but in very different amounts due to the superiority of synthetics. On another note, It is a truth that a 0W40 will require more VII's than a 0W200 oil. Generally speaking, the greater the spread, the more VII's will be needed to achieve it.

Next you said that VII molecules unwind making oil flow better when cold. Viscosity Index Improvers, or VII's actually improve viscosity. They "improve" or affect oil by making it "act" like it's a thicker oil. Anyway, ya got that backward. Vii's coil up when when cold, and therefore they have little or no effect on the oil at colder temps. It's when they get hot that they uncoil, and cause oil to flow much slower: that's when they have a huge effect on the viscosity of any oil, that is they "improve" it.

Not trying to sound like a know it all, but hoping to correct a couple small items here. But thank you again for all the light you shed on this subject in the rest of that great post.

One sample reference copied below:

Re: How do you know how much VII's in motor oil? [Re: CT8] #3557824 12/06/14 05:59 PM
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Posts: 41,756

The University implication that synthetics don't use VII is just plain wrong, as is the "10W30 is a 10W, VIIed to a 20, and can shear back to 10W)

It is possible to get multigrade performance from synthetic basestock, e.g. Amsoil SAE30 10W30, but you can bet that nearly every multigrade on the shelves has at least SOME VII.

It's not a bad thing...especially since they include HTHS minimums in the J300 specs these days (well for ages)...I just pick my lubricants in the mid-high VI, I have no reason to chase the 200s, as I think that they are going too far for a reasonable application....
 

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I may have gotten the behavior of the VII molecules backwards. I really don't think too much about VIIs.

Synthetic motor oil is made from Group III and IV base oil stocks that have uniformly sized hydrocarbon molecules and virtually none of the contaminants found in Group I and II base oils. The uniformity of the oil contributes towards its excellent performance, especially the low and high temperature performance.



The molecules are not very big but are very tough which is how the oil can flow well at cold temperature and yet protect the engine at high temperatures.


For synthetic oils their viscosity targets are often achieved without having to resort to the use of additives.These oils come by their good lubricity organically, so to speak.



Mineral based oils are a whole 'nother thing.


While it is possible to make mineral oils that have characteristics approaching those of synthetic oils, these mineral oils require additive packs that wear out and this limits the usable service life of mineral oils.



For instance a 10w-30 oil comes by its "30" viscosity index by the use of VIIs. The base oil is a 10 weight oil. As the VIIs wears out, breaks down, the oil returns to just being a 10 weight oil.

 

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Rockster,
Know what I was just thinking? Many of us remember the the oils we were buying back in the 60's during the muscle car era. But we realize now that those oils were inferior to the stuff being produced today. I wonder if an engine like our modern-day Hemi could survive on those oils? With it's close tolerances, big horsepower, and items like those special MDS lifters, I wonder how long a modern engine would last if we gave it a steady diet of 1960's era oil? Hmmm: API rated SD oil comes to mind

Ha... Anybody remember using a can opener to get the cans open? :)
 

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Cardboard oil cans with tin tops and bottoms. If you weren't careful, you could mangle the top, pull it off and have a big mess. You would be so angry after after cleaning up, you could forget to clean your church key before opening a cold one. The taste of 30 wt. reminded you of your second mistake. The good old days weren't always that good.
 

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Cardboard oil cans with tin tops and bottoms. If you weren't careful, you could mangle the top, pull it off and have a big mess. You would be so angry after after cleaning up, you could forget to clean your church key before opening a cold one. The taste of 30 wt. reminded you of your second mistake. The good old days weren't always that good.
I still have my oil can spout (the kind that punch through the top)
 

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Rockster,
Know what I was just thinking? Many of us remember the the oils we were buying back in the 60's during the muscle car era. But we realize now that those oils were inferior to the stuff being produced today. I wonder if an engine like our modern-day Hemi could survive on those oils? With it's close tolerances, big horsepower, and items like those special MDS lifters, I wonder how long a modern engine would last if we gave it a steady diet of 1960's era oil? Hmmm: API rated SD oil comes to mind

Ha... Anybody remember using a can opener to get the cans open? :)
By 50K you start noticing some oil consumption. Under hard acceleration some blue smoke.

Add some more miles and probably see blue smoke under decel (valve guide wear) and at hot idle some more lifter noise.

By 100k, start planning on a budget for rebuild as oil consumption has increased and peak power output is lower.

In the old days, many traded cars in after the warranty ran out and loan paid off (3 yrs loan term was typical then).

Between the tolerances and engineering of the era (soft rubber bushings); things starting feeling "less than new" after a few years.

Hop into a OEM quality restoration of a 50s - 70s car compared to today's.

A lot of play in the steering and loose feeling, body flex compared to what we've become used to as the standard today.
 
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