Motor Oil 103

First read 102:
http://ferrarichat.com/forum/showthread.php?p=134535392&posted=1

Motor Oil 103
Part Three. You have a synthetic mind.

Let us compare mineral and synthetic oils. I will not talk about chemical but rather functional differences. We discussed before how mineral oils are too thick at startup yet too thin when hot. The viscosity was corrected with the hot engine by adding VI improvers.

A 10W-30 multigrade mineral based oil is made from a 10 weight oil and has VI improvers added to thicken the product in a 212 F engine. It acts as a 30 weight oil when hot. It acts more as a 10 weight oil at startup. I remind you that a 10 or 5 or 2 weight oil is still too thick to provide lubrication at startup. They are all too thick at startup. There is currently no engine oil thin enough to operate correctly at startup. They all cause excessive wear at startup. Again, we are discussing the needs of my single hypothetical engine for around town driving.

Oil type.. Thickness at 75 F ..Thickness at 212 F

Straight 30..........250....................10
10W-30...............100....................10
0W-30.................40.....................10

Straight 10..........30.....................6
Straight 5...........20.....................4
Straight 2...........15.....................3
Straight 0...........12.....................3 est.

A 10W-30 synthetic oil is based on a 30 weight oil. This is unlike the counterpart mineral oil based on a 10 weight oil. There is no VI improver needed. The oil is already correct for the normal operating temperature of 212 F. It has a thickness of 10 while you drive to work. It will never thin yet has the same long term problem as the mineral based oil. They both thicken with extended age.

Synthetic oils are derived in the laboratory. They are pure, usually nearly clear. I describe mineral based motor oils as a distilled, concentrated product. The impurities need to be removed from the raw petroleum. These oils are therefore less clean and contain many impurities. Again, the problem is really more of theory than practice but the difference does exist.

People repeatedly say that synthetic oils are more stable in a hot engine. I hear that they lubricate better. The answer is yes and no. Oil molecules do not break down, just the additives. Generally, the synthetic oils do not have VI improvers so have less to lose.

There are some properties of synthetic oils that actually result is less wear than with mineral oils. These help increase your gas mileage as well. Due to a reduction of internal friction of the synthetic oil your engine will run a bit cooler. Wear increases as temperature increases, all other things being constant.

A main advantage that the synthetic has over the mineral based oil is the ability to lubricate at startup. Both types of oil have the same specifications at 104 F, 212 F and 302 F. It is the startup viscosity characteristics that separate these oils. Synthetic oils do not thicken as much on cooling. They have better fluidity as the temperature drops.

A synthetic oil that is labeled as 10W-30 is less honey like as a mineral based 10W-30 motor oil at startup. They both have a thickness of 10 at normal operating temperatures. At 75 F the synthetic is not as thick. At 32 F the difference between the two is even greater. At 0 F the mineral oil is useless yet the synthetic works fairly well. Just keep the RPM to a minimum.

At temperatures below zero you will not be able to start your car with mineral oils while the synthetic oils may be used to -40 or - 50 F. Oils are so thick that the normal method of viscosity measurement is not possible. Instead we measure if the oil can even be pumped or poured. Again, we are only discussing a single category of oil, the multigrade 10W-30 API / SAE grade.

I took an except from the web about Mobil 1 oils. They compared a 5W-30 synthetic Mobil 1 oil to a mineral based 10W-30 and a 10W-40 in ice cold conditions. The engine turned over at 152 RPM with the synthetic 5W-30 Mobil 1. The 10W-30 and 10W-40 mineral oils turned over at 45 and 32 RPM respectively. Neither of those engines started.

Motor oil becomes permanently thicker with exposure to northerly winter type weather. This is more of a problem to mineral based oils. Waxes form. This is why it is a bad idea to even store a bottle of oil in a cold garage. It goes bad on the garage self just because it is exposed to the cold.

To recap, synthetic oils have similar characteristics as mineral oils at operating temperatures. The synthetic oil will however be less honey - like at startup even though it has the same API / SAE rating. Yet the synthetic 10W-30 weight oil is based on a heavier 30 weight oil while the mineral based 10W-30 oil is based on a thinner 10 weight oil. They are both similar at operating temperatures yet the 30 weight based synthetic is actually less thick at startup and much less honey - like at low temperatures. This is the opposite of what common sense dictates.


This is worth repeating: The synthetic 10W-30 weight oil is based on a heavier 30 weight oil while the mineral based 10W-30 oil is based on a thinner 10 weight oil. They are both similar at operating temperatures yet the 30 weight based synthetic is actually less thick at startup and much less honey - like at low temperatures. This is the opposite of what common sense dictates.

As one can see this is no easy topic. Are you with me?

aehaas

 

I wrote this February:

There was an article from a University study on oil additives a ways back. Oils additives are of a few basic types.
1-More zinc. This is used in higher concentrations in racing oils. It builds up on metal parts under hot, severe, metal to metal conditions and may eventually decrease clearances. Prolong may be the example. It is OK if you keep rebuilding your engines.
2-PTFE, basically Teflon. It is good for nothing in my mind and clogs oils filters and ways decreasing oil flow and lubrication. If it says to shake well that means you got a problem off the shelft. Slick 50 I think.
3-Detergents. These increase performance in older, sludge filled engines by cleaning them out. Varnished parts are sticky.
4-It seems as there was another category.

In any event. Using name brand oil, gas and antifreeze is the best one can do. Any additive extras may destroy the basic chemistry of the home product. Owners manuals plainly state never to add additives.

aehaas

Smart people learn from their own mistakes.
Very smart people learn from other people's mistakes.



Does anybody know of the original article? Post here if you know where it may be located.

 

Regarding gel formation, a small except from SAE j300 1999:
4. Because engine pumping, cranking and starting are all important at low temperatures the selection of an oil for winter operation should consider both the viscosity required for oil flow as well and cranking and starting, at the lowest expected ambient temperature.
Pumping viscosity is a measure of an oils ability to flow...during the initial stages of operation. Test in ASTM D 4684. ....samples are tested after a slow cool cycle. This cycle has predicted as failures several SAE 10W-30 and 10W-40 oils which are known to have suffered pumping failures in the field after short-term (2 days or less) cooling. These field failures are believed to be the result of the oil forming gel structures that result in excessive yield stress and viscosity of the engine oil...

A.2.1...After preliminary warming, the sample is subjected to a controlled temperature/time cycle over 5 1/2 to 7 days. The cycle reproduces ...instability or reversion which has occurred during storage of oils in moderately cold cyclic conditions. Recent work shows relevance to engine oil pumpability failure. Oils exhibiting pour reversion have solids resulting from wax gel formation, at temperatures significantly higher than their ASTM D 97 pour points.

I use 5W-20 Pennzoil mineral based multigrade oil in my Expedition as it has many of the low temperature characteristics of higher weight synthetic oils. My '04 manual states that the SUV is delivered with a Ford semi-synthetic oil and although regular oil can be used they recommend a semi or full synthetic oil.

aehaas

 

Early synthetic oils leaked often. Now they are not supposed to do that in any engine. Old seals do leak however, just because they do not last forever.

I would like to pull an except from my chapter 7. This is for those people who say they need to look for older oils that were "designed" for that particular, older engine. My feeling is that you should always use the most current, highest rated engine oil:

This is from ASTM D 4485-03:
.....The SH rating was used in oils starting 1993. The SJ rating started in 1997 while the SL became effective in 2001 oils. According to ASTM D 4485, SL rated oils are superior to previous oils and from:
X2.3.1 and 2: SL oil is for use in current and all earlier passenger cars, sport utility vehicles, vans, and light trucks. This SL rated oil can be used in engines requiring SJ and all earlier categories.

aehaas

 

From spidr:
"a) I have heard the latest dino oils have lost some of the friction modifiers (zinc?) to help with emissions and such...I have been told to go back a rating or two for best lubricity and protection."

They have not lost them but concentration limitations were set. New, possibly better modifiers have been developed. In general each successive rating update is an improvement in most testing categories. I have never seen any test results go backwards, though some do not change.

I do not have all the specifics as yet.


From Chapter 7:
The American Petroleum Institute, API, and Society of Automotive Engineers, SAE, have rated engine oil performance over the years. We have seen the ratings go from SA, SB, SC, SD, SE, SF, SG, SH, SI, SJ, SL with SM to follow. There are over 3 dozen tests that oil now must pass in order to make the next higher rating. The tests are defined by the American Society for Testing and Materials, ASTM. Some tests have progressed to a zero tolerance level. For example there can be no sticking of any piston rings any more. I will compare the SL rated oil to the previous SJ oil in a few categories. For simplicity I will skip the units of measurement:


.......S J........S L......

.......30........20......maximum cam plus lifter wear
........9.........7.8.....sludge build up
........5.........8.9.....varnish rating
.......40.......26.4....maximum bearing weight loss
.......60.......45.......high temperature deposits
.......17.......10.......high temperature volatility

Other categories include: Resistance to rust, resistance to foaming, homogeneity and miscibility, flow reduction with varying amounts of absorbed moisture, gelation index and others.

As one can see just going from the previous SJ to the current SL rating is a significant improvement. I cannot wait to get the upcoming SM oil into my cars.


And from above I repeat:
I would like to pull an except from my chapter 7. This is for those people who say they need to look for older oils that were "designed" for that particular, older engine. My feeling is that you should always use the most current, highest rated engine oil:

This is from ASTM D 4485-03:
.....The SH rating was used in oils starting 1993. The SJ rating started in 1997 while the SL became effective in 2001 oils. According to ASTM D 4485, SL rated oils are superior to previous oils and from:
X2.3.1 and 2: SL oil is for use in current and all earlier passenger cars, sport utility vehicles, vans, and light trucks. This SL rated oil can be used in engines requiring SJ and all earlier categories.

aehaas

"I have been told to go back a rating or two for best lubricity and protection." This statement is wrong. For best lubricity and protection use the latest SL rated oils.

 

I went back a got some older data. Each year they seem to add more types of tests and replace outdated ones with newer, more relavent tests. Most tests are the same however in this time period:

...S H....S J........S L......

....64.....30........20......maximum cam plus lifter wear
....9.2.....9.........7.8.....sludge build up
.....5.......5.........8.9.....varnish rating (higher is better)
....20.....17.... ...10.......high temperature volatility

 

"Am I correct in saying that syn 10w-30 is a 30wt that flows like a 10 when cool and 10w-30 dino is a 10wt that flows like a 30 when hot??"



I'll answer it this way (rough numbers):

Mineral oil:
Oil type.. Thickness at 75 F .. at 212 F...at 302 F

Straight 30..........250....................10..........3
10W-30...............100...................10..........3
0W-30..........There are none in this range......



Synthetic oil:
Oil type.. Thickness at 75 F .. at 212 F...at 302 F

Straight 30...........100...................10..........3
10W-30.................75...................10..........3
0W-30..................40...................10..........3

aehaas

Your statement is correct for the grade of oil but the behavior is as shown above. The "thicker based" synthetic is thinner at startup.

A straight 30 weight synthetic acts as a multigrade 10W-30. It can be labeled either way.

 

"I believe this was the argument of the 10W-40 some time ago as the polymers added to get to the "40" inflicted weakness on the oil and the spread was too large"

This was a problem but no longer exists in todays oils. This is one of my problems, that people are stuck on old concerns that no longer apply. If you are stuck with this thought, then use the synthetic. The 10W-30 synthetic is based on a 30 weight oil and has no VI added. It cannot thin. It's only viscosity change with time will be to thicken.

The newer oils are not providing less protection because they are energy conserving. They are energy conserving because they provide better protection, reduce wear, reduce friction, reduce temperatures, are more fluid and lubricate better and evaporate less and et cetera et cetera et cetera. Please read SAE j300 and D 4485 if you are that concerned. I will bet you will go home and throw out every can of oil with an earlier rating from SL in disgust.

aehaas

 

Paul,
You really crack up my hydrocarbons.

Spidr,
Sorry, keep 'em coming. Sometimes I get carried away.

aehaas

PS- D 4485 defines 2 types of engines. 1-light duty-those engines generally used under less than peak output conditions. And 2-heavy duty-those engines generally used continuously at or close to peak output conditions.
Boats and airplanes, as well as a lot of industrial engines operate at heavy duty conditions. Just FYI.

Concerns about thinning of multigrade mineral based motor oils in heavy duty conditions are probably real, though I have not seen data about this in the descriptions of oil in general automotive applications. I would probably use a synthetic oil in my boat or plane just to be safe.