esters bad?

[GMorg]

I assume that extensive testing occurs for metal/oil compatibility, but esters still scare me. I can see the heat-stability benefits and maybe even some occasional cleaning benefits. However, esters can have the ability to dissolve metal oxides. Metal oxides can be very protective against further oxidation. Do we know that products like Motul and Redline are engine-safe for long, long-term use? I am speaking especially about time here, but miles matter too. Could these oils be removing lead and copper from softer surfaces and fittings?

I am not screaming that the sky is falling. I am just trying to determine if anyone knows (not assumes) or thinks (not believes) that esters are always a good idea for engines with multiple alloys and potentially long life-spans.

 

[goodvibes]

It's probably why RedLine shows higher Pb #s. I don't see it as an issue. If lead oxides are being removed, the used oil analysis are showing low enough amounts that it won't be an issue over the life of the vehicle. Your comments are actually encouraging regarding Redline as the lead #s in this case wouldn't be associated with bearing wear as Terry has often hinted at.

 

[Ray H]

The source for "esters can have the ability to dissolve metal oxides"?

 

[MolaKule]

quote:

---

However, esters can have the ability to dissolve metal oxides. Metal oxides can be very protective against further oxidation.

---

Never heard that one. What data do you have to back that one up?

Metal oxides in air can provide some protection but we are talking here about modern, advanced esters in hot engines.

Do some searching on iron sulphides, iron phosphides and additives in general, since they are responsible for forming protective layers.

Also, here are some recommended starting links:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000056#000000

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=4;t=000345

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000356#000000

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=21;t=000011

A Comphrehensive additive list:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=21;t=000032#000000

 

[GMorg]

Ray H, MolaKule,

I have not been able to find a direct reference for my earlier statement. All of my references are for aqueous solutions. Maybe I am mis-remembering or confusing facts. I therefore cannot currently defend my position and apologize for introducing the question without more homework.

However, I have found an a company that is making a similar (I grant different) comment about the use of ester oils in the context of refrigeration repair. Keep in mind the are providing a warning to users, not a claim about cleaning.

I would suggest that the esters used as refrigeration lubricants, with exposures to solder and copper line, is good evidence that these esters are compatible with soft metals.

From Copeland Corporations (http://www.copeland-corp.com/co/co_6_4_.htm)

"System Contaminants: Polyol Ester Oil (POE) is an excellent cleaner and will carry copper-oxides and other contaminants, that mineral oil left in place, through the system,
possibly clogging expansion devices. An inert gas, such as nitrogen, must be swept though the system to prevent copper-oxide formation during brazing."

 

[shavenstringer]

Esters Good.

 

[GMorg]

Ray H, MolaKule,

I have decided that I must be wrong about the mechanism of ester attack of non-ferrous metals. I can't find anything to back-up my memory of metal oxide solubility as an issue. However, in my search for support I came across several reports that esters do attack metals. The presence of water makes this worse. As a reference I offer an Army Engineering Manual (em1110-2-1424 28Feb99, Chapter 3, Table 3-1). In this list of characteristics of various lubricants it describes esters as being "slightly corrosive" and as having "enhanced corrosion in the presence of water". The table cites M.J. Neale, "Lubrication: A Tribology Handbook" as the primary source.


Please don't flame me. I am not trying to be argumentitive nor a smart a**. I just want to know if the benifits of esters are known to out-weigh potential problems. I am convinced that the jet industry requires them, a car with no coolant could use them, an overworked engine may benifit from them. But, should a collector use high-ester oils for example?

 

[MolaKule]

No flame taken, good discussion.

I suspect the Army manuals and M.J. Neale were referring to earlier diesters.

Modern polyol esters of pentaerithyritol and trimethylpropane have the best hydrolytic stability of any of the esters. Most esters have a very low TAN after manufacture.

The only way an ester could attack metal is for the ester to decompose under very high temps and lots of moisture, but we are talking the extremes of approx. 500 F. Since an ester is a reacted compound of fatty acids and alcohols, the fatty acid could attack after decomposition, but even the starting component fatty acids are very weak acids at best.

Esters are good cleaners because they have polar molecules that go down to the metallic surface and lift certain compounds.

 

[GMorg]

MolaKule,

I have tried to have a similar discussion in another thread, but have had no responses. From what I can tell, diesters are still in use.

http://www.neosyntheticoil.com/10w30.htm

In addition, diesters used in compressor oils do have warnings about imcompatibilities with certain metals - particularlly zinc.

http://www.fammllc.com/famm/lubricant_product.asp?compressoroils&complete&CetusDE100

So, without an ingredient list on the bottle, how can the average Joe make a logical decision about additives and boutiques that tout esters? Please don't suggest that all manufacturers known what they are doing. Also, please don't suggest that if an engineer is involved that everthing will be ideal. I have had engineers tell me that they don't need to know the answer to a question if they can look it up. (One was responsible for designing cooling systems for nuclear reacters, the other was responsible for evaluation/testing of jet engines prototypes.)

Am I just left "trusting"...?