Synthtic cleaning properties

[kickster]

I have been reading that synthetic oil keeps the engine clean. Which property of synthtic oil is responsible for cleaning?

Do all synthetic have this properties? What about synthetic oils that are not true synthtics?


PS. What does PAO mean?

 

[Bill Morris]

Use a dino oil and compare with synthetic...it'll clean your nozzles

 

[TallPaul]

Excellent question kickster. Let's see what the BITOG experts say. Meanwhile I will ramble so they have something to correct

.

My understanding is that the synthetic oil really does not clean out a dirty engine, but is pretty good at preventing a clean engine from getting dirty.

Probably a heavy duty motor oil, with its high detergency, would do a better cleaning job. But some synthetics may clean, primarilly esters (Group 5), but only certain ones. Redline Oil is Group 5 but their techs tell me it really doesn't clean your engine.

The other synthetics are either Group 4 (PAO like Mobil 1) and Group 3 (the one for which the synthicity is debated to no end). Group 4 is better than Group 3 but not by a whole lot, and Group 5 is supposed to be much better. PAO is poly alpha olefins or something like that.

 

[Jelly]

Synthetic oil keeps an engine clean because it resists breaking down like a conventional/mineral PCMO would.

PAO stands for polyalphaolefin, which is a group IV base stock.

 

[Dr. T]

Again, where are the experts?

I always thought that the synthetic esters had an affinity for metal, thereby displacing dirt/sludge, etc. and this is what accounts for the cleaning properties seen.

 

[Pablo]

I think the "cleaning effect" of most synthetic oils is:

a) way overblown, at least on non-bearing surfaces. This can be seen typically in a 200K mile plus engine on dino. Switch over to synthetic....sure the syn. oil will darken quickly but the surfaces in the engine will take a long time to clean, if ever. Then switch back to dino, do a double AutoRx clean and WOW the engine really cleans up.....and once again back to synthetic and the surfaces look really clean.

b) I think bearing surfaces or contact surfaces of seals do get cleaned better with synthetic.

 

[T-Keith]

Synthetics won't break down as much as dino oils, therefore leaving less "dirt"(oxidation, wear particles, ect.) They also tend to have a better addative package, therefor more cleaning aggents.

-T

 

[dickwells]

Not an expert here, but can give some pretty strong anecdotal evidence: I bought an 88GMC 1/2 ton at 67K miles, it was smoking like the valve seals were bad. Took off the Rocker covers and found a heavy coat of sludge, scraped off what I could and blew down the drain holes. (The thermostat was stuck open and I replaced it) Started running M1 5or10W30 at 5Kmile intervals. At 115 K I had the rocker covers off to adjust a couple of lifters. The heads were spotless. I still have the truck and it has about 220K miles on it. Starts and runs good but still smokes and I have recently switched to Penz long life in 10W40 as it is in backup service now. Regards

 

[systema]

I'm only a rookie, but in my opinion:
sludge build up in one oci =
amount of oil broken down - amount of sludge particles dispersant and cleansing agent handled.

So base on the equation, a syn. oil will absolutely reduce the amount of oil breakdown, thus the dispersant/cleaners may be able to deal with more old sludge instead of keeping stressed to prevent further sludging up. A probably better additive package may also increase the amount of sludge that can be removed.

For a dino HDEO, it possibly improved slightly in the first factor, but the amount of sludge that it can handle is greatly increased, thus sludge created during one oci may be at a negative value.

And for the cleansing effect of ester, I reckon it's due to its solvency.

 

[TC]

Oil spec sheets confirm that, in general, synthetic oils have significantly higher TBNs than dino, and mixed fleet "diesel" lubes such as Rotella are significantly higher than syns. If you're primarily looking for cleaning capability, and not as concerned with syn performance, go with mixed fleet and save a few bucks. TBNs for three 10w-30 oils:

Kendal GT-1: 6.2
Kendal GT-1 Syn: 7.9 (10.1 for 5w-40)
Shell Rotella: 11.5

 

[ekpolk]

quote:

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Originally posted by TC:
Oil spec sheets confirm that, in general, synthetic oils have significantly higher TBNs than dino, and mixed fleet "diesel" lubes such as Rotella are significantly higher than syns. If you're primarily looking for cleaning capability, and not as concerned with syn performance, go with mixed fleet and save a few bucks. TBNs for three 10w-30 oils:

Kendal GT-1: 6.2
Kendal GT-1 Syn: 7.9 (10.1 for 5w-40)
Shell Rotella: 11.5

---

Interesting. The TBN for the Mobil-1 that's approaching 5,000 miles service in my wife's Sequoia is still at 6.9 (just tested, posted in the UOA section).

I've seen in a number of different places that certain syn base stocks do have inherent detergency. For automotive applications, the diester bases, such as used in Neo, are the most aggressive cleaners. The POE (polyol esters, like used in RedLine) are supposed to be almost as good. PAO, while generally an excellent base material, is only mildly detergent, as compared to the esters. Group-IIIs and Dino oils are only as detergent as the additives put into them.

Real Experts: did I get that pretty much right???

 

[JohnBrowning]

THe esters do not clean like a detergent. THe ester want to attach themselfs to the metal more then the sludge wants to attach to the metal. So if the sludge is more displaced from the metal then it is cleaned from the metal. The problem then is that once it is detached from the metal were is it going to go? Esters do have a lot of solvency though. If it weakens the "glue" holding the carbon together the carbon can be cuaght by the filter if big enough but were does the "Glue" polimerizered VII's go?

My opion is that even with something like Redline of Motul 300V if you had a really sludged up engine you would be looking at 25,000 miles to completely clean it it out just by running the oil through it. Now if you have an engine that is just varnished and the varnish is really soft as in just becomeing a problem then it is a different story.

WHen certain esters are bonded to the metal surfaces it does not leave any place for the "glue" to stick too. It is also not that common to have many if any VII's in a product loaded with esters. If you are not continuely adding more sludge precusors to the pot eventaly all of the old one get flushed out of the engine.

Getting sludge in an engine is like getting fat. It does not happen over night! Once you get fat you have to continue to do what ever you did to get fat in the first place to stay fat. It is easier to stay in good shape then it is to get back into shape. Like wise it is easier to keep the engine clean to begine with then it is to chemicaly clean it out. TO date the best product for cleaning out sludge is Auto-Rx!

 

[Gene K]

Mobil recommends that if you switch over a car to synthetic later in its life:

1. Normal change to synthetic with no flush.

2. Change oil after 2500 ml.

3. Change oil after an additional 3500 ml .

4. Change oil at maximum recommended interval.

Reason given is that the oil will gunk up from old deposits due to cleaning action of Mobil 1 for first couple of cycles.

Is Mobil recommending needless oil changes to sell more oil?

Gene

 

[Drstressor]

Those are good answers by Elkpolk and John Browning. The ester components of synthetic oils are primarily added to increase the polar solvent properties of the PAO base oil. This allows the additive package (anti-wear, anti-oxidation, friction modifiers, and detergents), which are primarily polar molecules, to stay in solution. A secondary effect of esters is that they will make soluble previously oxidized material (sludge) that has precipitated out on surfaces because of the presence of polar molecules. The job of the detergent additives, which are salts of organic acids, is to hold the oxidized material in solution.

If you switch an engine that already contains a large amount of sludge over to a synthetic oil, the sludge will gradually be solubilized by the ester components of the oil over time. This leads to faster than normal depletion of the available detergents, which will be reflected by a more rapid decrease in TBN. So shorter initial change intervals following a switch to synthetic oil makes good sense.

 

[Bill Morris]

If a vehicle was to use synthetic oil say from 10k miles and reach to say 150k, would it be a good idea to flush the engine or would the synthetic oil prevent any type of build up from what has been described as above?

 

[Losiho]

quote:

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Originally posted by JohnBrowning:
THe esters do not clean like a detergent. THe ester want to attach themselfs to the metal more then the sludge wants to attach to the metal.

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Am I missing something here ? Isn't Auto RX concentrated Esters ? Or is it a different type of Esters ?

 

[JohnBrowning]

The esters used in motor oils are normaly synthetic esters. Auto-Rx is made up of natural esters. So it is not an apples to apples comparison.

 

[Losiho]

Thanks for the explanation JB