… and that’s why in general it is better to use the highest number before W your vehicle can safely use, while the number after W is pretty much what manufacturer prescribes for the engine: less viscosity index improves => less shearing effect
having option to put 0W30 / 5W30 / 10W30 into my Altima, I’m mostly using 10W30 in relatively mild Virginia climate; similarly selecting 5W20 in place of 0W20 for Mazda3 (I would gladly use 10W20 if they sold it)
still, the viscosity index is probably dwarfed by more important factor of selecting a proper oil for the application
I do not promote Amsoil (although they are doing quite good products!), but when promoting “their stuff” they publish some curious pieces like this:
So, even for one 5W30 index, the range of wear, cold performance, antiwear additives quantity and even viscosity is quite high, if not said “all over the range”
If somebody cares to dig in these numbers, I would be curious what top 3 brand/type combinations from what a “regular” (non-racing, 12K miles a year) owner can buy in a store would be selected ?
I have my favorite around top in all tests and buy it as 10W30 and 5W20 off Wallmart shelf
Hint: it is not M-1
Sorry, I don’t see that at all. The paragraphs I quoted are consistent with the number AFTER the W as changing. The number before the W seems less likely to decrease any further.
This quote from the link is consistent with my understanding:
Viscosity modifiers are polymeric molecules that are sensitive to temperature. At low temperatures, the molecule chain contracts and does not impact the fluid viscosity. At high temperatures, the chain relaxes and an increase in viscosity occurs.
Figure 1 shows how an SAE 10W30 retains the low-temperature properties of an SAE10 (providing the low-temperature pumpability), while the additive gives it the characteristics of an SAE30 at higher temperatures (providing the protection of a thicker oil film). The SAE 10W30 is made by blending a viscosity modifier with an SAE10 base oil, and there is actually no SAE30 involved.
Also, a higher number before the W means more viscous oil at ‘cold’, startup temps. Doesn’t seem necessarily good in all cases.
sorry, looks like I made a long and windy statement
my point is:
you pretty much know the coldest temperature you will expose you car to
select the highest “before-W-number” you can live with (example: in Alaska you likely need 0W, in Florida you can safely have 10W or 15W)
the higher the “before-W-number” is, the thicker base oil stock will be and less viscosity modifiers oil will have
the less modifiers it will have => the less shearing effect
still, my second idea was that this logic will probably give only few percent improvement over the “elephant in the room”, which is the set of additives particular oil brand would have
ok, but without knowing the rate/mechanism of breakdown for the modifiers, using a higher before-W-number might not help.
For example, if breakdown of (identical) modifiers in 10w30, 5w30 and 0w30 is always at a rate of X number per heat/shear cycle, the ‘30 weight’ portion of the oil is going to go down the same way in all three oils.
I would strongly suspect that amount of viscosity modifiers will be the lowest in 10W30 and the highest in 0W30 for obvious reasons, so I would suspect that breakdown rate will also deviate proportionally
assuming 10W30 is of SAE10 stock and 0W30 is from SAE0 stock (which is unlikely to be true), at very high mileage the breakdown “finish line” will also be more forgiving to the motor requiring SAE30 at operating temperature
I also expect more modifiers in 0w30 vs 10w30.
Yet I don’t know that the modifiers are identical between the two, and I don’t know that they breakdown at different rates.
Here I have to agree: we can not know for sure if the same type of modifier is used…
To defend my theory I can only tell that 0W30 will likely need more “heavy weight” polymers, which tend to shear more, but I have to tell this statement is not backed by any factual data
But it’s kind of fun . . . because he seems to get mighty upset when somebody disagrees with him, and even more so when the same person repeatedly disagrees with him
basically, it relates to the fact that oil simply evaporates when on the cylinder walls, so the lower it is, the better
5W20 has definite advantage over 0W20 and 10W30 over 5W30
I discovered it first on my Subarus, which tend to burn oil in undue quantities and once I transitioned to low Noack oil types, this effect became substantially less, to the point I neglected to check oil level between my usual 5,000 miles OCI
I don’t agree with likely, in part because of this from the link:
Lower molecular weight polymers are more shear-resistant, but do not improve viscosity as effectively at higher temperatures and, therefore, must be used in larger quantities.
IOW, smaller modifiers/polymers can be used in larger quantities in place of larger modifiers/polymers to some extent.
if we assume that we have to have much more of viscosity modification (like 0w30), then it is likely you will use “heavier artillery” (AKA “higher molecular weight polymers”) to get effect you need, as likely it is a a limited %% of the base stock you can substitute with viscosity modifier, so…
#1: if both 0w30 and 10W30 are to use the very same polymer type => 0W30 will have more if it, it will shear faster
#2: if 0W30 uses heavier weight plymers => it also shears faster
One big difference is that 0w30 will always be synthetic and will always flow better on cold startup, e.g. where most engine wear happens.
0w30 is closer to the correct viscosity of a operating temperature engine so the engine will be more efficient earlier.
You’re probably right that a 10w30 oil will last longer over an extended oil change interval, but what’s the point if there is increased engine wear every startup? The 0w30 oil will stay close to its rated viscosity for over 10k miles according to many oil analysis tests.
sounds like you are ok with trading less evaporation for higher ‘cold’ start viscosity that was discussed at the link:
For instance, in the crankcase, an oil with a low viscosity at low temperature is needed so the oil pump can push the oil to the top of the engine during those cold morning starts.
ah.
seems you see this in terms of ‘decisive winning argument’. I don’t.
I use ‘maybe’ when I have no basis to attach an estimate, and ‘likely’ when I have basis/confidence for at least a 51 to 49 guesstimate. You “likely” use the words differently.
YES, I’m perfectly good making this tradeoff, plus I made a disclaimer of using your best judgement about the cold performance REALLY needed for your vehicle
I think manufacturers tend to recommend 0W20 or 0W30 nowadays since in general it tends to imply using a synthetic basestock as @yellowbal told above and makes them to answer less questions
