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IF AN ENGINE HAD that pressure with non-syn, what ever the pressure is with synthetic IS WHAT IT WILL BE WITH SYNTHETIC, unless all the clearances are adjusted for the change. Does this make sense?
To me, No, it really doesn't make sense at all.

The hot viscosity of an oil is what will eventually determine hot oil pressure. This will differ between oils (not all oils with a weight of 20W50 have the same hot viscosity) but is not really a function of Synthetic vs. Conventional oil composition.

The viscosity it typically measured as cSt @ 40º C (cold) and cSt @ 100º C (hot).

What I am really saying is that it's the numbers, not whether an oil is Synthetic or Conventional, that determines what the oil pressure will be.

One of the benefits of a good synthetic is that it will not shear down out of it's grade with heat and/or high RPM use. Some (note I did not say all) conventional oils have a problem with this. For an example, a 20W50 oil that has sheared down would only have the hot viscosity of a 10W40 oil.

Joe
 

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To me, No, it really doesn't make sense at all.

The hot viscosity of an oil is what will eventually determine hot oil pressure. This will differ between oils (not all oils with a weight of 20W50 have the same hot viscosity) but is not really a function of Synthetic vs. Conventional oil composition.

The viscosity it typically measured as cSt @ 40º C (cold) and cSt @ 100º C (hot).

What I am really saying is that it's the numbers, not whether an oil is Synthetic or Conventional, that determines what the oil pressure will be.

One of the benefits of a good synthetic is that it will not shear down out of it's grade with heat and/or high RPM use. Some (note I did not say all) conventional oils have a problem with this. For an example, a 20W50 oil that has sheared down would only have the hot viscosity of a 10W40 oil.

Joe
Hi Joe,

I know it's *supposed* to be that way, but it's not always true. I know that if you take a 5 weight synthetic oil and a 5 weight conventional oil, and pour either one of them on a frigid winter morning, the synthetic will flow *much* better than the conventional oil. But, in theory, it's not supposed to.

Fwiw,

bs
 

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I know it's *supposed* to be that way, but it's not always true. I know that if you take a 5 weight synthetic oil and a 5 weight conventional oil, and pour either one of them on a frigid winter morning, the synthetic will flow *much* better than the conventional oil. But, in theory, it's not supposed to.
Brian,

I agree 100% with you there. Cold pour point is one area where synthetics have always performed much better than conventional oil. But cold pour point is not one of the tests used to determine oil weight (IIRC), where hot and cold viscosity are.

My point was more to this: If a synthetic 20W50 oil produced radically higher oil pressure when hot (versus a conventional 20W50), that would mean the hot viscosity was really high (and the oil really isn't a 20W50).

There is a range of viscosity allowable for an oil to be classified as a 50 wt. If the hot viscosity is above that range, then the oil would need to be labeled as a 20w60, not a 20W50.

Joe
 

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Brian,

I agree 100% with you there. Cold pour point is one area where synthetics have always performed much better than conventional oil. But cold pour point is not one of the tests used to determine oil weight (IIRC), where hot and cold viscosity are.

My point was more to this: If a synthetic 20W50 oil produced radically higher oil pressure when hot (versus a conventional 20W50), that would mean the hot viscosity was really high (and the oil really isn't a 20W50).

There is a range of viscosity allowable for an oil to be classified as a 50 wt. If the hot viscosity is above that range, then the oil would need to be labeled as a 20w60, not a 20W50.

Joe
But isn't cold pouring an indication of cold viscosity?

I'm asking the question, not trying to make a statement..

bs
 

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But isn't cold pouring an indication of cold viscosity?
Yes, but remember the cold viscosity standard (cSt @ 40º C) isn't done at a very cold temperature.

There are hundreds of other measurements that can be taken both hot and cold, but I was simply focusing on the ones that are used to determine an oil's grade.

Back to my point:

Within that grade there is variation, but not enough to make a synthetic oil of the same weight produce pressure readings that are too high for an Alfa engine, compared to a conventional oil of the same grade.

Joe
 

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Within that grade there is variation, but not enough to make a synthetic oil of the same weight produce pressure readings that are too high for an Alfa engine, compared to a conventional oil of the same grade.

Joe[/QUOTE]

I believe that is exactly what I was trying to say Joe. You DID explain it better!
Best, :DGordon Raymond
 

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Incidentaly, the viscosities of the two mentioned oils are as follows:

Mobil1 15W50 red cap 18.1 cSt @ 100C
Valvoline 20W50 racing 20.5 cSt @ 100C

50wt is defined by SAE as 16.8-22.7 cSt @ 100C. Both are plenty thick at engine temp (especially considering some folks run 40wt!)
 

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Discussion Starter #28
The 15W50 weight that I used was only available in the EP version, and over a couple of oil change intervals with the new EP formula I noticed both of the Alfas were burning a little more oil than usual and hot oil pressure wasn't great.

My poor results with the EP formulation of Mobil 1 15W50 and the suggestions that it is no longer a Group IV synthetic were enough to get me to switch to Redline 15W50 - which has been performing very, very well (Zero oil burning and better hot oil pressure).

Joe
From your observations and my observations I would say that you and I are in somewhat of an accord. I haven't seen any usage yet as I only have about 100 miles on the fresh oil. I lean in your direction about the base stock being to thin as Valvoline 20-50 Racing oil is of a higher base stock, hence it would have better oil pressure. This might be also true of the Redline having a heavier base stock to start with. I might switch over to the Redline before I go jerking parts out here and there that might be alright.


BS...I agree about the oil pressure to a point that to much is a killer and to little is also a killer. Little Red Riding Hood says there has to be just enough in the middle somewhere to make life congenial. :) I hate low oil pressure, as that can be a precursor to a blown #4 rod and that is expensive...synthetic or not.
 

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I wouldn't mind running 15w-40 Delo 400 all the time since I think it's a VG (subjective) oil and I like the idea of the 15W lubing abilities at start-up - but I wonder about it's shear characteristics when hot. All the Blackstone tests I've had done on 3 vehicles show viscosity down from what it should be. The oils tested were Mobil 1 5w-30, Syntex 10w-30 and GTX 20w-50. I haven't done an analysis on the Delo 400 (yet) but attached is the analysis of the Alfa's GTX 20w-50 after 1200 miles. Blackstone said "Oil viscosity was a little light but that's not hurting anything." I do not fully understand their comment. In any event, I like the margin of error a 50w gives if it shears down.
 

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Discussion Starter #30
I finally have some time to delve into this issue some more now that vacation weekend has passed, company is gone and school is letting me out early instead of 2 hours after school for meetings. I bought some new plastiguage and measured the #1 and #2 cam caps for clearance. The two are between .0015 and .001 inches. I am not sure what the clearance should be, at this point I am going on the assumption that these are in tolerances.
Tomorrow I am going to put in Valvoline 20-50 syn and see what the results are.

Is there a website where it spells out what base stock is used in which oil so one can make an informed decision as to which is heavier?

From what I am reading, a group III base stock is heavier than a group II. That would be like using 10w (group II) and 20w (group III) as to where you start building your oil product?

One would think that 20w would be 20w motor oil, but the base stock seems to be the dividing difference between the brands. One would also go on the assumption that a 20w-50 has the same viscosity range as any other 20w-50 but this doesn't seem to be the case from what I am deducting here. Correct?

I am still thinking that the oil pump is the culprit in all of this and I haven't ruled that out.
 

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Discussion Starter #31
Here is a couple of good pictures that show how plastiguage should work. :)

I will measure the remaining caps tomorrow and I am suspecting that they will all spec out.
 
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