syn. oil

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  #41  
Old 05-27-02, 08:52 PM
marturo's Avatar
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Join Date: Jun 2001
Posts: 1,448
The smoke is clearing.

So If I get this right. Since I don't have any trouble starting in winter with 20-50 oil. The 20 -50 oil would be better for me as an all season oil than a 30# for winter and a 40# for summer.

20-50 oil is 20# at let's say 10 & in the hot summer doing a little stop light hopping the weight will be 50# providing me with a better cushion between moving parts.

Now it is not the petrolem that is becoming a 50# when it is hot. So how or what is it that makes the oil thicker when hot? Also does this additive come apart when it is cold so the lubricant runs like a 20# oil?

This is what has kept me wondering just why I should use the multi grade oils. I bought a new Ryobi 4 cycle weed & brush cutter. In the package came a small bottle of 30# weight oil. Of course the manual says use a 30#.

My son who was brought up on multi grade oil uses 20-50 in all his 4 cycle small engines claiming they protect better than the factory reccomended 30# oil. Whos right? After all the same company says to use 32 to 1 & I have been using 100 to 1 Mobil 2 cycle synthetic oil.

It may seem easy for you Dan with the test equipment and testing data. However it is a bit confusing for the DIYer with only our gut feeling that this is working better than this or that.

I bought a brand new Makita Chain saw and read where you could use a 50 to 1 mix or 100 to 1. So of course I wanted to run the 100 to 1 and asked for the oil named in the book. Sorry sir we don't have that oil it has not been imported into the US.

This is when I called Mobil. I told them about the Synthetic oil in the Makitia book. Then I asked since they had a synthetic oil could I follow the MFR recomended mix using synthetic oil. They said yes if Makitia said 100 to1 with a synthetic oil then by all means use that mix with Mobil.

Now after 2 years I must say that every 2 cycle I own is using a 100 to 1 mix & the plug is spotless no carbon build up whatsoever. I have the oil bath filter ready to mount and will sell the K&N filter as cheese was right I read a few articals about flow & micron size. The oil bath wins. I am also looking into the 2 filter system that the second or overflow filter takes out down to 1 micron. Now I think I will have to run a synthetic with no additive package our else using regular oil the 1 Micron filter will take out the addatives. The link I posted where the guy says that you have to have a synthetic oil formulated for extended oil change periods like 25,000 miles. Also while Mobil 1 is synthetic it is formulated for more frequent changes.

I hope someone is taking notes because it is getting a bit more like a science project than I would have thought. I do want an oil that will go 25,000 miles if possable. I also would like to find ammunition that you could fire and not have to clean your gun for 1000 rounds. No kidding a gunpowder that left no carbon or ash & and a bullet that cleaned your bore and kept it from rusting.

Marturo
 
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  #42  
Old 05-28-02, 05:55 AM
sciguyjim
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Exclamation Trying to clear the smoke

Dan,

An oil classified SAE 10 weight will be a certain viscosity at 100 degrees C. This will be thinner than a 10w30 oil. A 10w30 oil is classified as an SAE 30 weight at 100 degrees C. A SAE 30 weight monograde and 10w30 multigrade oil will have the same viscosity at 100 degrees C.

Marturo,

If you can start fine with a 20w50 oil in the winter and it isn't too thick when warm either, then go ahead and use it. You said:
"20-50 oil is 20# at let's say 10 & in the hot summer doing a little stop light hopping the weight will be 50# providing me with a better cushion between moving parts."

The 20w50 oil will not be 20 weight when cold. Just look at a bottle some winter day, it will be very thick, not 20 weight. When it warms up to 100 C, the 20w50 oil will be the same viscosity as a 50 weight oil at 100 C.

Your next question: "Now it is not the petrolem that is becoming a 50# when it is hot. So how or what is it that makes the oil thicker when hot? Also does this additive come apart when it is cold so the lubricant runs like a 20# oil?"

It's the viscosity index improvers that make the oil remain thick when hot. They are long molecules that get tangled up at hot temps and keep the viscosity high. At low temps the molecules curl up to a smaller size and this lets the viscosity go down. BUT, at the low temps the oil will naturally thicken, it's just not the VI improvers that are doing the thickening. Also, the pour point depressant will be helping keep the oil this at low temps.

In another place you state: "I am also looking into the 2 filter system that the second or overflow filter takes out down to 1 micron. Now I think I will have to run a synthetic with no additive package our else using regular oil the 1 Micron filter will take out the addatives. "

There is no need to worry about the 1 micron filter removing any additives. The additives are all molecular in size, VERY much tinier than 1 micron. They will stay in the liquid, only solid particles will be filtered out.

Here's how my reference data explains multiweight viscosity:

"Most people believe that a 5w30 oil is good for cold weather because it is a 5 weight oil in cold temps and a 30 weight oil at high temps. On the surface this might seem to make a certain amount of sense. Naturally, a 5 weight oil would flow better than a 30 weight oil. This would make it ideal for cold temp operation.

Nevertheless, this is a profound misunderstanding of what the labeling means. The two numbers really have little to do with each other. The final number is based on the kinematic viscosity at 100 C, as for monograde oils.

So, if a multigrade oil, when heated to 100 C, falls within a certain kinematic viscosity it is classified as a certain SAE grade (the last number- like the 30 in 5w30.) In other words, the kinematic viscosity of a 5w30 multi-viscosity oil falls within the same range at 100 C as a monograde SAE 30 weight oil does.

The first number (the 5 in 5w30) is only a relative number which basically indicates how easily it will allow an engine to turn over at low temps. It is NOT a viscosity reference. In other words, a 10w30 is NOT a 10 weight oil in cold temps and a 30 weight oil in warm temps.

In fact, since SAE viscosity classifications only apply to an oil at 100 C, it doesn't even make sense to label it as a certain SAE viscosity at any temp other than 100 C.

Besides, if you thought about it for a second, it wouldn't make sense for a 10w30 oil to be a 10 weight oil in the cold and a 30 weight oil in warm temps. What liquid do you know of that gets thicker as the temp increases or thinner as the temp decreases?

I would venture to say you probably can't come up with one. This holds true for motor oil as well. If a 10w30 was a 30 weight at 100 C and a 10 weight oil at cold temps, that would mean it thinned out at the temp dropped. That just doesn't make any sense considering what we know about liquids. It just doesn't happen like that.

The fact is that a 5w30 motor oil is THICKER in cold temps than in warm temps. However, a 5w30 motor oil will be thinner than a 10w30 motor oil when subjected to the same low temp conditions - because the "w" number is lower. This is an indication of better cold weather performance. In other words, a 5w30 flows better in cold weather than a 10w30 motor oil will. Think of the "w" as a "winter" classification instead of a "weight" classification.

Results from the Cold Crank Simulator (CCS) and Mini-Rotary Viscometer (MRV) tests are used to determine the oil's "w" grade. The better the engine "startability" of the oil at low temp, the lower the "w" classification. Each "w" grade must meet certain "startability" requirements at a specified temp.

For instance, a 0w grade oil must have a maximum CCS centipoise (cP) value of 3250 @ -30 degrees C as well as a maximum MRV cP of 60,000 @ -40 degrees C. A 5w grade oil must have a maximum CCS cP value of 3500 @ -25 degrees C and a maximum MRV cP of 60,000 @ -30 degrees C. The lower the cP value for both specifications, the better. (Different oils will have different CCS cP values, so you want to choose the one with the lower CCS cP value. - my note.)

Notice that the 0w grade oil is tested at a lower temp on both tests AND must still have a lower CCS cP value than a 5w oil which is tested at a higher temp. As a result, a 0w30 will allow your vehicle to start easier on a cold morning than a 5w30 will. Likewise, a 5w30 oil will pump easier in cold temps than a 10w30 oil will.

Nevertheless, at 100 degrees C, they all fall within the same kinematic viscosity range. Therefore, they are all classified as SAE 30 weight oils at 100 C. In other words, after your car has warmed up, a 0w30 and 10w30 motor oil are basically the same thickness (within a certain SAE specified range.)"

"...For instance, lets look at a 5w30 motor oil. In order to flow well enough to meet the 5w classification, a petroleum oil would start with a very thin basestock (maybe one that would be classified as an SAE 20 weight if heated to 100 C.) Then that basestock would be combined with pour point depressant additives."

"...But, in order to meet the requirements to be classified as an SAE 30 oil, something must be done to assure that this oil won't thin out to its 20 weight basestock viscosity at 100 C. The oil must be "built up" using long chain, high molecular weight polymers (called Viscosity Index Improvers)...

These polymers expand as temp increases counteracting the natural thinning action of heating an oil. So instead of thinning to a 20 weight classification, the oil only thins to a 30 weight classification.

NOTE: Remember, don't let the 5w fool you. It's not a viscosity classification. It's a classification to establish that an oil will flow adequately at cold temps to protect your engine. The oil is still THICKER at cold temps than it is at hot temps. The oil WILL thin as the temp increases. The only question is how much. VI improvers reduce this thinning action to acceptable levels so the oil can meet both the 5w and the SAE 30 requirements."

I hope this hasn't been too long, but I think it's good to try to clear all this up.
Jim
 
  #43  
Old 05-28-02, 07:50 AM
Joe_F
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Cool

Folks,

I'm closing this one up. The original poster's questions have been answered.

Suggest we take this one elsewhere if we want to discuss it so as to clear up some bandwidth for new posts
 
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