tnord

so i'm flipping through the HRP catalogue (you'd like it Scot) looking at their prices on REM procedures for a ring/pinion and as usual stopped to look at the various oils they offer. neo has been particularly intriguing to me ever since the guy who qualified 2nd at the runoffs in FA and builds/maintains most of the FA/FC/FF cars in the region recommended it to me.

of course they had the prerequisite redline offerings. i've always noticed that they offer typical 5w30, 10w30, 15w50, as well as 30wt, 50wt, etc. but what is the benefit/cost of these "single weight" oils? i assume it is a tradeoff type of deal, where the dual weights will protect better when cold, but not as well at temp. and the single weights protect better at temp at a cost of lower effectiveness upon startup.

[cliff clavin voice] what's the deal with single weight oils? [/cliff clavin voice]

Knestis

Dual viscosity oils are designed for the real world, where cars have to operate - as you point out, start up - over a huge range of oil temperatures. In Chicago, my father-in-law's car's oil is going to increase temp by 200*F or more pretty much every day, and have to flow across the range.

Single weight oils are less of a compromise for a narrower operating range. Particularly if you have an oil pre-heater on a dry sump, it's not necessary for oil in "real" race cars to flow at low temperatures.

K

CRX Lee

So how many people here realized that the "W" in 10w30 actually stands for "winter" and not "weight"?

Doing video work with Valvoline for nearly a decade, I sat through a lot of motor oil training info. The multi weights are definitely for a real world usage across wider ambient and operating temperature range.

Crx Jimmy

multi viscosity oils can break down under stress and heat and lose viscosity, which you dont want if you are racing, single weight oils in general have a higher tolerance for breakdown

Grumpy

Multigrade oils typically begin as base oils, such as 10W. Then viscosity-index modifiers (polymers) are added in an effort to stabilize the viscosity. This allows a 10W40 oil to flow like a 10W at cold temperatures and a 40W at higher temperatures.

The multigrade oils' viscosity modifiers are long-chain molecules that lessen the change of viscosity with temperature variance. In the past, the polymer additives (used to thicken the oil) were sometimes susceptible to viscosity loss. Permanent viscosity loss occurred when high shear forces (such as the relationship between the main bearings and the crankshaft) actually break the polymer molecules into less-effective smaller pieces. On a similar note, temporary viscosity loss also occurred when the polymer molecules aligned themselves in order to create a path of least resistance.

Fortunately, today's additive packages have improved oil's shear-resistance. However, oils with the same rating from different manufacturers can exhibit different viscosity ratings in an operating engine, depending on the shear stability of their viscosity-modifying additives.

For technoids, weights are defined thusly (stokes and centistrokes are measurements of viscosity):

"SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or 10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the minimum of 9.3 cSt and a maximum of 12.5 cSt.

"SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt and a maximum of 16.3 cSt.

"SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt and a maximum of 21.9 cSt.

"SAE 60 is SAE 60 no matter what the "W" prefix number is: 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 21.9 cSt and a maximum of 26.1 cSt.

"There is no SAE 70 and no one is likely to make one with a "W" prefix number although it is possible using a synthetic base oil. This viscosity is identified as Grade 70. The viscosity @ 100 degrees C has a minimum of 26.1 cSt and no maximum."

The difference between a multigrade and a singlegrade oil: The singlegrade can't pass the low temperature viscosity test. If it did meet one of the following "W" viscosities, it would be a multigrade.

Singlegrade oils will become obsolete for performance engines in the future. We dropped SAE 30 and SAE 40 because SAE 10W40 does everything 30 or 40 can do—and some things the straight grades can't do—like increasing horsepower. If an off-roader doesn't like 10W40, then use 20W50. It can do everything a 10W40 can do except pass the sub-zero viscosity test at -20 degrees C.

Multigrade viscosities are run at six different sub-zero temperatures. When a racing-oil designer puts a formula together, he has to know the viscosity at 100 degrees C of every component in the additive composition. He has to have a target viscosity objective for the finished oil in each SAE grade. Once a formula is established, the technician who supervises the blending has to duplicate this formula in the correct proportions every time the product is blended. The viscosity at 100 degrees C has a plus or minus written into the oil's quality-control specification.

Multigrade or Multi-Vis?

One oil manufacturer claims that "some people in the industry use multi-viscosity as if it means the same thing as multigrade. An oil cannot be multi-viscosity, but it can be multigrade by meeting the viscosity requirements for SAE 30, 40, 50 or 60 and one of the sub-zero "W" viscosity requirements. At one time, some oil companies labeled oils SAE 10W, 20W30—as if the oil could be 10W and 20W at the same time. This is impossible because 10W is measured at -20 degrees C and 20W is measured at -10 degrees C, which eliminates the multi-viscosity theory."

stevel

ok, i'm confused. So, for a race car could I go with a straight 30W during race season, since it's never going to see the cold temperatures? Is there any benefit? Or are today's 10W30's good enough that I don't need to bother with the single weight. Do single weight oils have a higher tolerance for breakdown?

steve

tnord

very helpful grumpy....thank you.

correct me if i'm wrong in my summary.
the single weight oils were created to combat the problem of the polymer molecule chains breaking apart (or aligning themselves) under shear forces at a given temperature (100d C). the developers of these single weight oils focused on that temperature range and that temperature range only when construding the formula. because of this focused approach they don't pass tests for viscosities at lower temperatures.

my next question would be, on various states of engine build, where is the line drawn where the added protection at operating temp (when racing) outweighs the cost of wear at cold startup?

production based engines used only in a racing environment (dedicated HPDE car)?
production based engines that are b&b'd in a racing environment (racing cars based on SS rules)?
production based engines that are b&b'd, overbored, higher comp, other mild prep (IT cars)
racing engines (Formula Atlantic, SWC, etc)?

Grumpy

Accusump pre-oiler????

tnord

not legal per our rules. although yes, that would solve the problem.