Well, I see the myth
continues.
Let me start by saying that my '69 Mopar 383magnum runs on Pennzoil 10w-40, and has since
day 1. And believe it not it hasn't turned into a molten lump of junk yet. It actually has 137,000 fairly aggressive miles, runs very strong, and is
very clean inside.
The original point of this thread was to highlight the fact that todays 10w-40(dino) is
unjustly looked down upon.
And, to prove it
has the goods to "deliver".
One or two examples of "shearing"(or anything) isn't strong evidence to refute this; and
possible planned obsolescence is irrelevant.
It's all about hard data + UOAs + visual parts inspection!
I performed a crude comparision of viscosity "shear-down" for dino non HM 5w-30, 10w-30 & 10w-40 over 3-5K miles. Using the UOA section I randomly(except 10w-40; there
were only 8) chose 8 samples. Before averaging I threw out the highest and lowest readings.
Averages :
5w-30: cSt at 100*C
8.54
10w-30: cSt at 100*C
9.53
10w-40: cSt at 100*C
12.27
I then averaged the
beginning viscosities(per PDS) of the test brands:
5w-30:
10.7
10w-30:
10.7
10w-40:
14.2
Which gives us the amount of original viscosity retained:
5w-30:
80%
10w-30:
89%
10w-40:
86%
I did this to prove to myself, as well as others that 10w-40
can compete with 10w-30 in these terms!
quote:
Would be interesting to see side by side tests of how the two hold up under stress. Which would suffer the most permanent viscosity collapse and which would produce the most sludge? Would the thicker Group I base hold up better than the thinner, Group II fortified oll or vice versa?
Yes, this
is interesting! I'd like to contrast the two on
all aspects. The oil companies probably have some "old papers" that speak about this; wonder how we can lay our hands(or eyeballs) on them?
quote:
I am not sure of this but I suspect you could be correct that the same basestock is used and the higher viscosity is achieved not only through viscosity modifiers, but by some kind of size exclusion process that would increase the amount of higher molecular weight component in the 10w-40. In general I think it safe to assume that your thermal properties, i.e. Noack and FP should improve with higher Mw. However, if the Mw blend isn't narrow enough and overly broad with a lot of viscosity modifiers, I think one could easily lose the added bonuses of the increase in high Mw components. I think these properties may be very dependent on the processes each company using to obtain their multi-grade oils. I will throw this out there and see the responses I get--It isn't necessarily the average molecular weight of the base stock oil, but the narrowness/breadth of the molecular weight that may have the biggest effect on your thermal stability.
This makes alot of sense. So, this is essentially what each step up in group means; a
narrowing of the MW range. Then, within each group there resides various weight(MW) oils that are blended to achieve the desired viscosity and characteristics.
I'm catching on now! Chevron base oils
TallPaul,
Very nice UOA!
I think Citgo should work great with AutoRX; because it's mostly group I. FWIW, their HM(UltraLife) has one superb additive pack.
BTW, those 300cid last forever.