Synthetic: Use the LOWEST 1st number available ?

[lomez]

....so long as the second number matches the manufacturer's recommendation.

For example: The manufacture recommends 15W-50 for my area and temp. Then, I personally would use a 0W-50, so long as it also had the appropriate API service.

Can anyone who really understands oil punch a hole in that one??

My rationale- first, the manufacturer is doing 2 things by recommending the 15W-50. First, they have determined that a 50weight oil is best at operating temperature (212 F). Second, they are assuming you're using mineral oil, not synthetic. Since we know that a mineral oil of 15W50 rating would really be a 15 weight oil, with additives that will cause it to THICKEN when it gets warm, while a synthetic of 15W50 is really a 50weight that just happens to flow like a 15 weight when "cold", why would anyone intentionally (other than the $$$ issue) select a synth oil with a first number (cold flow) greater than zero??

My theory is, since we know that, when "cold", a motor oil of 15weight will NOT flow properly (when cold, neither does a 10 or a 5 or even a 0, to be honest), I want to use as low a number as possible. Ideally, I'd want a -10Wxx synthetic. THAT could be perfect....but also expensive, and perhaps impossible to formulate.

For now, in ANY vehicle I own, I use synthetic 0W-xx, where the "xx" is the actual recommended weight per the manufacturer. In my motorcycles, I run Eneos 0W-50 with SM API service (while the manufacturer recommends 20W-50 in summer).

 

[brandini]

I thought the wider the spread the less likely it is to stay in grade- a la ACEA ratings that have stay in grade requirements.

 

[lomez]

we're talking about synthetic though. It's my undertanding that NO (and someone correct me if this is not correct), NO synthetic uses modifiers in order to manipulate viscosity.

Thus, while a mineral oil of 10W30 is really a 10 weight with modifiers to thicken it with heat, up to a 30......a synthetic IS a 30, with NO modifiers, but which flows just as well as a 10 when "cold". Now, perhaps this is not true, in the case of synthetics, when the gap gets out to a 0W-50??

 

[aquariuscsm]

Originally Posted By: brandini
I thought the wider the spread the less likely it is to stay in grade- a la ACEA ratings that have stay in grade requirements.


^^That`s always been my understanding as well. The shorter the spread,the more base oil and less modifiers/thickeners.

 

[lomez]

I thought pure synthetics never have modifiers. ?

 

[chevrofreak]

Nearly all multigrade oils, including synthetics, use viscosity index improvers. One of the only exceptions to that is Red Line, but they still use VII in some of their oils.

 

[lomez]

I've heard the EXACT opposite. I've read, in many, many places, that pure synthetics NEVER use any form of viscosity enhancers? Not saying you're wrong, just that I've read the exact opposite, even from Bob "the oil guy"

In fact, here's the statement directly from Bob:

"Synthetic oils are a whole different story. There is no VI improver added so there is nothing to wear out. The actual oil molecules never wear out. You could almost use the same oil forever. The problem is that there are other additives and they do get used up. I suppose if there was a good way to keep oil clean you could just add a can of additives every 6 months and just change the filter, never changing the oil.

When the additives wear out in a synthetic oil it still has the same viscosity. It will not thin as a mineral oil. The fear that some say Porsche has that oils thin when the VII runs out is not applicable to these synthetic oils. These oils will always have the correct thickness when hot and will still be too thick at startup as with all oils of all types, regardless of the API / SAE viscosity rating."
[color:#3333FF][/COLOR]

I assume the "additives" he's talking about are the detergents, etc. He specifically says there are NO viscosity enhancers. Thus, a 0W50 will ALWAYS be a 50 weight, even 10 years later (assuming no gasoline blow-by).

 

[IndyIan]

Originally Posted By: lomez
we're talking about synthetic though. It's my undertanding that NO (and someone correct me if this is not correct), NO synthetic uses modifiers in order to manipulate viscosity.

Thus, while a mineral oil of 10W30 is really a 10 weight with modifiers to thicken it with heat, up to a 30......a synthetic is a 30, with NO modifiers, but which flows just as well as a 10 when "cold". Now, perhaps this is not true, in the case of synthetics, when the gap gets out to a 0W-50.

I've only read here that Redline has straight grade synthetics with no modifiers that meet multigrade specs. I think most/all? synthetics off the shelf use some sort of viscosity index improvers to make up their multigrade oils.
Is a conventional 15W50 worse than a low price 0W50 synthetic for losing grade? Probaby has more to do with the VII's than the basestock in each oil.
In winter going with a lower cold grade oil is probably always better for good flow at start up. In the summer, I think it depends on your usage.

 

[aquariuscsm]

Wouldn`t a multi grade HAVE to have some kind`ve modifiers? It seems it`s either a 10 wt,5,wt,etc.........it just can`t exist as two totally different entities without some kind`ve chemical munipulation/modification.

 

[chevrofreak]

Originally Posted By: aquariuscsm
Wouldn`t a multi grade HAVE to have some kind`ve modifiers? It seems it`s either a 10 wt,5,wt,etc.........it just can`t exist as two totally different entities without some kind`ve chemical munipulation/modification.


They can exist without VII. Base stocks with very high viscosity indexes do not need as much VII, and if blended correctly, none at all. Red Line 5w-30 uses no VII, and is made from polyolester and polyalphaolefin base stocks, and has a viscosity index of 162.

 

[Jeffs2006EvoIX]

This will be a good one

 

[lomez]

as I understand it, and per Bob, synthetic (pure) is different. If flows very easily when cold, regardless of actual weight. So, a 10w40 synthetic, IS a 40weight oil, but flows, when cold, just like a 10weight mineral oil would. It does this naturally, and without any modification. Thus, nothing to degrade (in terms of viscosity anyway), and you're never running less than a 40 weight.

A 10w40 mineral IS a 10 weight oil, with modifiers to thicken when warm, up to the equiv of a 40 weight. Over time, these modifiers degrade and you're running a 10 all the time.

I can find no reason not to run a synthetic 0w-50 in engine where the "manual" calls for a 20w50. Seems to me, the 0w-50 would be many, many times better, and probably reduce wear 300-500%, while having zero downside. But then.....that's what I'm trying to find out for sure.

 

[chevrofreak]

Originally Posted By: lomez
synthetic (pure) is different. If flows very easily when cold, regardless of actual weight. So, a 10w40 synthetic, IS a 40weight oil, but flows, when cold, just like a 10weight mineral oil would. It does this naturally, and without any modification. Thus, nothing to degrade, and you're never running less than a 40 weight.

A 10w40 mineral IS a 10 weight oil, with modifiers to thicken when warm, up to the equiv of a 40 weight. Over time, these modifiers degrade and you're running a 10 all the time.

I can find no reason not to run a 0w-50 in engine where the "manual" calls for a 20w50. Seems to me, the 0w-50 would be many, many times better, and probably reduce wear 300-500%, while having zero downside. But then.....that's what I'm trying to find out for sure.


At one point that may have been true, but they were using base oils with very poor viscosity indexes compared to what we have today. Most modern oils use Group II at a minimum, and many are II+, or a II and III blend. That gives them a very decent viscosity index, which will require less polymeric viscosity index improvers to meet both the hot and cold specs of a given grade of oil.

http://en.wikipedia.org/wiki/Lubricant#Base_oil_groups

 

[1999nick]

Come on, guys. NO oil thickens as it gets warm. All oils get thinner as they get hotter.

 

[Quattro Pete]

Originally Posted By: lomez
A 10w40 mineral IS a 10 weight oil, with modifiers to thicken when warm, up to the equiv of a 40 weight.

This sentence is worded a bit inaccurately. No oil thickens when warm. It would be more correct to say "with modifiers to prevent it from thinning as much as 10w oil would when warm".

Quote:

I can find no reason not to run a synthetic 0w-50 in engine where the "manual" calls for a 20w50. Seems to me, the 0w-50 would be many, many times better, and probably reduce wear 300-500%, while having zero downside. But then.....that's what I'm trying to find out for sure.

I guess it depends on a particular oil and how it's formulated. Take for example the Castrol 10w-60 oil that's used in some BMW applications. Despite being a synthetic oil, it thins to a 40-weight fairly quickly when put into service, as observed by the UOAs that we've seen on it. Even oils as stout and well regarded as M1 0w-40 tend to thin out to 30-grade in service. Not that this would cause anyone's engine to blow up or anything...

But basically, the higher the spread, the less viscosity stable the oil. It may be less noticeable when it comes to synthetic, but it still happens.

 

[lomez]

Originally Posted By: 1999nick
Come on, guys. NO oil thickens as it gets warm. All oils get thinner as they get hotter.


Yes, that's true of course. I guess I phrased it wrong. The oil doesn't get thicker in absolute terms. It (mineral) thins less, relative to the increased temp. So, if it flows like a 10 when cold (because it really is a 10), at 212, it flows like a 40, BUT in absolute terms, the oil is thinner than it was when cold.

that clear as mud now?

 

[A_Harman]

Some synthetics don't have VII's, most famously the ester-based oils such as Redline and Motul. But even Redlines 0wXX's have some VII's. Motul advertises all of their 300V series as having no Viscosity Improvers, and they limit the grades to:
0w20
5w30
5w40
15w50
20w60

See the pattern? By the time they get to a 50-weight, even the inherently high VI of the ester base stock only allows formulation of a 15w50 grade. If they wanted to get a 0w50, they would have to add polymer to get there. Here is where the oil loses its shear stability. You may start out with a 0w50, but run it for a while, and it will turn into a 0w40.

If the manual is calling for a 20w50 conventional, I would not go lower than 15w50 synthetic to get maximum shear stability.

 

[lomez]

Originally Posted By: Quattro Pete
Originally Posted By: lomez
A 10w40 mineral IS a 10 weight oil, with modifiers to thicken when warm, up to the equiv of a 40 weight.

This sentence is worded a bit inaccurately. No oil thickens when warm. It would be more correct to say "with modifiers to prevent it from thinning as much as 10w oil would when warm".

Quote:

I can find no reason not to run a synthetic 0w-50 in engine where the "manual" calls for a 20w50. Seems to me, the 0w-50 would be many, many times better, and probably reduce wear 300-500%, while having zero downside. But then.....that's what I'm trying to find out for sure.

I guess it depends on a particular oil and how it's formulated. Take for example the Castrol 10w-60 oil that's used in some BMW applications. Despite being a synthetic oil, it thins to a 40-weight fairly quickly when put into service, as observed by the UOAs that we've seen on it. Even oils as stout and well regarded as M1 0w-40 tend to thin out to 30-grade in service. Not that this would cause anyone's engine to blow up or anything...

But basically, the higher the spread, the less viscosity stable the oil. It may be less noticeable when it comes to synthetic, but it still happens.





well put.

 

[lomez]

Originally Posted By: A_Harman
Some synthetics don't have VII's, most famously the ester-based oils such as Redline and Motul. But even Redlines 0wXX's have some VII's. Motul advertises all of their 300V series as having no Viscosity Improvers, and they limit the grades to:
0w20
5w30
5w40
15w50
20w60

See the pattern? By the time they get to a 50-weight, even the inherently high VI of the ester base stock only allows formulation of a 15w50 grade. If they wanted to get a 0w50, they would have to add polymer to get there. Here is where the oil loses its shear stability. You may start out with a 0w50, but run it for a while, and it will turn into a 0w40.

If the manual is calling for a 20w50 conventional, I would not go lower than 15w50 synthetic to get maximum shear stability.


excellent answer. makes sense! That sucks though, inasmuch as a 15W cold number, is really high. Thus, I would expect very little protection, and therefore, tremendous (in relative terms) wear while the motor is cold. This is why I wanted to go to a 0W50. But, I suspect 40 (where you suspect it will degrade to) is too weak when hot.

 

[Jjones]

I always looked at an oil such as 5w30 as being neither a 5weight or a 30weight.I thought it is a oil that will not thicken past a 5weight when cold and not thin past a 30weight when hot.