0W-40 in 1970 Cadillac Eldorado

Hence the word "approximately."

At 110C

By the very factor you pointed out, the actual thickness depends on where both the straight 30 and and the 10w30 fall within the allowable range at the measurement temperature.

Reply to
Steve
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I was disagreeing with your statement that they would be the same AT OPERATING TEMPERATURE. They won't and even at the benchmark temperature you can easily tell the difference.

-jim

Reply to
jim

The point I made was this. Using the identical benchmark testing that Texaco and independent labs used to compare Havoline 10 w 30 to other major brand 10 w 30 oils that showed a slight advantage to Havoline, when coaxed to compare Havoline 10 W 30 to Havoline straight 30 - the straight 30 had a significant advantage. What wasn't much discussed was some testing Shell did with identical motors with very sensitive temperature sensors. Engines that were run for thousands of hours. The multiweight oils did not fare well at all. The "stress" testing is still the benchmark for testing oil. To this point, the new Castrol Edge is by a significant margin the best performing oil on today's market. But as I said, do not expect Exxon Mobil to take this laying down. Like Arnold - they'll be back with an even better oil.

Better living through chemistry.

Reply to
krp

We had a 1983 Mercury Cougar. We loved the car, but it needed regular repairs and died at 99,960. (Yes, as a matter of fact, I *did* contemplate renting a Clydesdale to pull it the other 40 miles . . . but we were packing for grad school, and I just got rid of it.)

Anyway, it called for 20w50 in its factory handbook. Then again, it called for three different oils throughout the year in some climates. I think I got away with only two here in Las Vegas.

hawk

Reply to
hawk

That is _simply_ _not_ _true_.

In just about 30 seconds of web searching, I found the spec page for Royal Purple oils (I'm not promoting RP oils, just found this example and they are API certified oils unlike some other botique synthetics).

At 100C (the benchmark temperature), their 5w30 oil has a viscosity of

11 centistokes, but their straight SAE 30 is *thinner* at 10.6 centistokes! And their 10w30, while thinner than the 5w30, is still slightly thicker than the straight 30 weight, at 10.8 centistokes.

Furthermore, the 5w30 has a VI of 157, but the SAE 30 only has a vI of

119, which tells me that you can go WAY above the benchmark temperature and the 5w30 will remain thicker than the SAE 30.

Here's the link, knock yourself out:

formatting link
click "Product Sheet" for the PDF.

Reply to
Steve

Well no it simply is and was true. Your originally statement that at operating temperature the viscosity of 10w30 is the same as 30 w is still false. Does that mean you can't google and find some oil company advertisement. Well of course you can find advertisements no body said you couldn't.

Your original statement is still false. Most of the 30 weight oil tends to have higher viscosity than most of the 10w30 at operating temperature. This is not speaking of some ideal car and oil. It is just how things generally work in the real world where most of the cars on the road don't use synthetic oil and many operate with oil temps higher than 100c on hot days.

**There is a allowable range for viscosity at the standardized temps. **The economics physical realities of producing motor oils for sale puts most of the 10w30 at the bottom of the allowable viscosity range and the 30w at the top. **Most engine oil operates at a temperature above 100C on hot summer days

Those facts combined make it generally incorrect to state (as you did) that the

30w and 10w30 oil will have the same viscosity at operating temperature.

-jim

Reply to
jim

I never actually said that, I said that they would be "approximately" the same, and that means that the 30 could be either thinner or thicker than the 10w30 at operating temperature, depending on where operating temperature falls in relation to the SAE benchmark temperature.

You, however, claimed that (quoting from text reprinted above), "He is correct that 10w30 will be thinner than straight 30 in the typical car on a typical summer day," and that is what is categorically false. If you assume that the 30 and 10w30 are within a small percentage of the same viscosity at the benchmark temperature, then the 30 will have to be *thinner* than the 10w30 as you go above the benchmark temperature because it has a lower viscosity index (in other words, a steeper slope to its temp. vs. viscosity curve).

That much is just math.

Does that

Specification sheet, not advertisment. And you can go look up similar numbers for Pennzoil Platinum, Castrol Syntec, GTX, Edge, Mobil 1, Mobil conventional, Kendall, Delo, Rotella, etc. etc. Brand doesn't matter.

See above, this is the part of your argument that is the most incorrect. It is in fact, generally backwards. You seem to think that 30 weights will stay thicker at higher temperatures, but the opposite is in fact true. The simple combination of the fact that the 10w30 and 30 wt. have to be pretty close in viscosity at the benchmark temperature, and the fact that the 10w30 has a higher VI *generally* means that the 30 wt. will be significantly THINNER than the 10w30, not thicker, at temperatures above the benchmark point. It will be thicker when the engine is COLDER than the benchmark temperature.

What makes things interesting is that today it is quite possible to formulate a synthetic oil that meets the requirements for, say, a 10w30 rating and to do it *without* any viscosity index improvers at all. Synthetic base stocks in both group III+ (eg, Shell XHVI base used in Rotella and Pennzoil Platinum and similar stock used by Valvoline and others) and group IV (such as PAOs used by Mobil, Royal Purple, Amsoil, Shaeffers, etc.) have inherent VIs of 140 and higher now. That means that the oil company could, if they wanted to, sell it as a 30 weight as well. And if they do have to add some VIIs to create a multigrade oil of, say, 5w40, then the amount needed is so extremely small that there's very minimal benefit, if any, to the single grade oil. Its not like the old days where making a 10w40 required such a large percentage of VIIs that they, not the base oil, dominated the deposit formation and degradation characteristics of the product.

Reply to
Steve

No not approximately the same -they will be noticeably different. It will be noticeable in oil pressure and in the way that it will drain from the oil pan.

You believe this because you rely only on glossy brochures for information?

Reply to
jim

So you keep saying. Dig that hole deeper if you want, I'm done.

No, I believe it both because the math predicts it and because measurements prove it. If you don't believe me, go over to one of the oil forums and pose the question. Make it simple, ask them if a 30wt will be thinner or thicker than a 10w30 at temperatures significantly above 100C.

I'm done beating the dead horse, Jim. You can have the last word now if it'll make you feel better.

Reply to
Steve

The math is based on a simplistic model that is little more than taking 2 points and drawing a line thru them. The model is designed to do not much more than prove a claim to the simple minded and it does that as long as one is willing to completely ignore the real world.

What measurements? You have provided only 2 measurements for one particular brand and that comes with a caveat that you may see some variance from the measurements in the actual product. You are talking about one particular brand of synthetic that has a tiny tiny share of the market. That is pretty thin soup you are calling proof.

-jim

?If you don't believe me, go over to one of the

Reply to
jim

Its not a line, its a curve.

But apart from that the "simplistic model" also happens to be EXACTLY correct for a Newtonian fluid, which is precisely what defines a straight-grade oil (no viscosity index improvers are permitted in straight-grade rated oils). Therefore, the only deviation from the model in the "real world" will be for the non-Newtonian fluid, which the multi-grade may or may not be depending on whether it has VII additives or not. Assuming it does, then it's viscosity will always be higher at high temperatures and lower at low temperatures than the Newtonian fluid up to the temperature at which the VIIs disintegrate, but by then both oils are oxidizing as well! Assuming that it does not have VIIs, then the "2 point" model is also correct for *it* at the high end (the low end may still be non-Newtonian because of pour-point depressant additives) and the two curves will never cross again above the temperature at which the two fluids have equal viscosity (which in the example is already BELOW the 100c benchmark).

Duh.

Chosen only because they make their data readily available and popped up first on a Google search. It also happens to be representative of all PAO-based synthetics in this regard, there's nothing special about it. In fact in doing a little more research, that brand's multi-grade oils are apparently considered in the thin side and prone to shearing for their rating, so in that sense they are a bad case for my argument. Pick any brand you want, or pick a different brand of straight from multi-grade. Go ahead. Find a counter-example! Please! Its quite likely that you can find at least one combination of oils that meet your criteria, especially since so many of the synthetic single-grades could easily qualify as multi-grades if dual rating were allowed. I didn't find such an example, but then I didn't go looking very hard for the oddball counter-example that may be out there.

At least I produced actual numbers instead of just waving my hands and saying the same thing over and over Lloyd Parker style. Or talking about how you "notice it when it drains out of the pan," which means that its already well below the 100C benchmark for one thing, and I seriously question your eyeballs as an accurate measure of viscosity for another. If my soup is thin, yours isn't even soup yet.

I'm really done this time.

Reply to
Steve

Right it is a curve not a line. And you haven't a clue as to what the formula for the curve is in reality. But that doesn't stop you from pretending you are making a mathematical calculation. All you have really done is read some glossy brochures and are parroting the buzzwords that you read therein.

What an idiot. If you actually did have even a smattering of understanding of the math you would recognize that I am saying the 2 curves never cross - that is in most comparisons the 30 weight is always going to be thicker than the 10w30 at any temp that you might find in an engine crankcase. I don't know (and neither do you) what the formula is for either curve but it is obvious that they do not intersect. Since you don't actually have a precise formula for the curve for either type of oil it is just babbling nonsense when you claim you can prove your point using mathematics.

Maybe for some particular well chosen examples it will cross at a point below

100C. But in general if you compare what is most commonly available on the market and what is commonly used in engines that won't be the case.

It is not as if all oil comes in perfect discrete steps of 10 20 30 40 weights. These are categories describing a range. And even in your fancy brochure that you offer as proof, there is a disclaimer to that effect.

Nothing special except it is not what is in most engines on the road. And in part that is why it costs more than what most people use.

You mean I should go find my own glossy brochures?

Who is loyd parker? Another wannabee mathematician?

I'm not the one that made the bogus claim with nothing believable to back it up. I'm perfectly happy with the information I get from observing a pressure gauge or watching as it pours thru an opening. You on the other hand keep insisting that the crap you read in glossy brochures is mathematical proof. Did it ever occur to you that no company ever puts anything but the information that casts them in a good light in their advertising literature? So if a company does make a product that is a cut above average they are going to try to promote that as selling point and put it in their advertising.

HA HA HA

-jim

Reply to
jim

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