kennith said:
All the specs are wonderful, but given this engines wonderfully silly design in many aspects, I wonder just what it might prefer in viscosity, if it could have anything it wanted. Living in NC, with high humidity, and temperatures eclipsing 100 on occasion, and in the winter occasionally dipping into the teens, it is a fairly broad range to cover. As well, with my common winter trips to PA, things can change on occasion, though I rarely note anything below zero these days.
I guess I'm just wondering if people consider 10w30 simply not cutting it. I'm interested in that European formula, but that is a bit of a change from what I am currently using.
Cheers,
Kennith
Ugh, I keep timing out replying to this. Let me add as I go here.
xWxx ratings should hold little value in the big picture.
First, lets look at that viscosiry is and how its measured.
-20oC/-4oF to -40oC/-40oF extremely low temperature cranking, pumping and low shear viscosity (SAE W)
100oC/212oF low shear viscosity (SAE)
150oC/302oF high temperature high shear viscosity (HTHS)
The SAE W viscosity is an extremely low temperature rating based on the ability of an oil to be pumped and allow engine cranking at -20oC/-4oF to -40oC/-40oF.
See figure one
The Pumping requirement insures a minimum amount of oil pumping capability at a given temperature. The temperature is 30oC/-22oF to for a SAE 10W rating, 35oC/-31oF for an SAE 5W rating and -40oC/-40oF for an SAE 0W rating.
General Motors has a more stringent pumping requirement. A GM 6094M approved SAE 5W-30 is required to have better pumping capability at 35oC/-31oF than other SAE 5W-30 products. GM has similar improved pumping requirements for 0W and 10W ratings. This more stringent GM requirement
insures that oil will reach critical areas of the engine sooner during low temperature starts. Even though the test is performed at extremely low temperatures, a related benefit is generally expected at more moderate temperatures.
There are also minimum cranking requirements. These must be met at 25oC/-13oF for a SAE 0W rating, 30oC/-22oF for a SAE 5W rating, and 35oC/-31oF for an SAE 0W rating.
An SAE 5W-20 must meet the exact same extremely low temperature pumping requirements as an SAE 5W-30 or an SAE 5W-40. A GM 6094M approved SAE 5W-30 is required to have better extremely low temperature pumping characteristics than an SAE 5W-20 that is not GM 6094M approved. These
ratings do not have the ability to indicate which product might tend to flow better a more moderate temperature of 16oC/-60oF.
The standard SAE viscosity rating indicates the low shear kinematic viscosity at 100oC/-212oF. It also sets minimum standards for high shear viscosity at 150oC/-302oF.
See figure two
The standard SAE viscosity rating indicates the ability of the oil to flow at 100oC/-212oF. It also sets minimum requirements for tolerating high shear rates at 150oC/-302oF.
The 100oC/-212oF flow requirements are very broad. The difference between an SAE 20 and an SAE 30 can be insignificant. Likewise, the difference between an SAE 30 and an SAE 40 can be insignificant. The range for an SAE 30 goes all the way from 9.3 centiStokes and 12.5 centiStokes
http://www.sizes.com/units/centistokes.htm at 100oC/-212oF. A 9.3 and a 12.4 are both regarded as SAE 30. But, a 12.5 is an SAE 40 and a 9.2 is an SAE 20.
The accepted range for the 150oC/-302oF high shear test is even greater. An SAE 20 can be anything over 2.6 centiPoise.
http://www.wisegeek.com/what-is-centipoise.htm An SAE 30 only has to be slightly higher at 2.9 centiPoise. And, an SAE 40 is not required to be any thicker than an SAE 30 in this test.
SAE 20 products (including 5W-20 and 0W-20) can be as thin as 5.6 centiStokes. But, they are almost always over 8.5 centiStokes. There is good consistency in this viscosity category. Unfortunately the SAE 30 category (including 0W-30, 5W-30 and 10W-30) does not share this consistency.
This creates a great deal of potential for confusion and engine damage within the SAE 30 category. Some SAE 5W-30 products are well below 10.0 centiStokes at 100oC/-212oF and barely over 2.9 centiPoise at 150oC/-302oF. Other SAE 5W-30 products are over 12.0 centiStokes at 100oC/-212oF and well over 3.5 centiPoise at 150oC/-302oF. These two extremes in actual viscosity both carry the same SAE 5W-30 rating. But, they are NOT appropriate for the same applications. The thinner 5W-30 will flow better and cool pistons and piston rings more efficiently. The thicker 5W-30 will provide better high shear force protection.
The ACEA rating system separates the SAE 5W-30 category approximately down the middle. Anything under 3.5 centiPoise at 150oC/-302oF can qualify for ACEA A1/B1, A5/B5, C1 or C2 approval but can NOT qualify for ACEA A3/B3, A3/B4, C3 or C4 approval. Any product over 3.5 centiPoise at 150oC/-302oF can qualify for ACEA A3/B3, A3/B4, C3 or C4 approval but can NOT qualify for ACEA A1/B1, A5/B5, C1 or C2 approval.
The ACEA rating system also contains other very stringent requirements. Some ACEA ratings indicate greatly enhanced ability to tolerate extended oil drain intervals. Some ACEA ratings indicate an ability to improve fuel efficiency (even beyond the API Fuel Conserving rating). And, some ACEA ratings indicate different levels of catalytic converterprotection (including some more stringent than ILSAC GF-4).
A/B: gasoline and diesel engine oils, note anything refeering to diesel is for the B rating.
A1/B1
Oil intended for use in gasoline and car + light van diesel engines specifically designed to be capable of using low friction low viscosity oils with a High temperature / High shear rate viscosity of 2.6 to 3.5 mPas.s. These oils may be unsuitable for use in some engines.
A3/B3
Stable, stay-in-grade oil intended for use in high performance gasoline and car + light van diesel engines and/or for extended drain intervals where specified by the engine manufacturer, and/or for year-round use of low viscosity oils, and/or for severe operating conditions as defined by the engine manufacturer.
A3/B4
Stable, stay-in-grade oil intended for use in high performance gasoline and direct injection diesel engines, but also suitable for applications described under A3/B3.
A5/B5
Stable, stay-in-grade oil intended for use at extended drain intervals in high performance gasoline and car + light van diesel engines designed to be capable of using low friction low viscosity oils with a High temperature / High shear rate viscosity of 2.9 to 3.5 mPa.s. These oils may be unsuitable for use in some engines.
Lets look at Mbil Products as a example.
extended Performance Mobil 1 10W-30 is 10.7 cSt at 212F and 3.1 cP at 302F.
The extended Performance Mobil 1 5W-30 is 11.0 cSt at 212F and 3.1 cP at 302F.
The regular Mobil 1 5W-30 is 11.3 cSt at 212F and 3.09 cP at 302F.
The regular Mobil 1 10W-30 is 10.0 cSt at 212F and 3.14 cP at 302F.
All four of the above products have the same A5/B5 long life approval. They all have very similar hih temperature (302F) viscosity. At 212F theyr are all similar but the regular 10W-30 is the thinnest and the regular 5w-30 is the thickest (surprise).
Im starting to geek out a little here, but at the end of the day the Xw-XX rating has much less value then the HTHS rating. At temp, that 0-40 will give bter protection then a 10-30. Check the chart on figure 3.