HDEO Combustion Chamber Cleaning Mechanism

[OMCWankel]

In using the search engine on this forum, I consistantly run into threads that mention HDEO oils ability to clean, and keep clean, the rings, combustion chamber and exhaust ports of gas and diesel engines.

I have found the same HDEO results on sites that specialize in Mazda Rotary motors, engines that have seals instead of rings, and burn oil by design.

I was wondering if any of the knowledgeable members of this forum could explain to me the actual mechanism of this combustion chamber cleaning action?

This forum is the best knowledge base on lubricants I have ever found.

Thank You All

 

[Drew99GT]

Just a guess, but oil is designed to slip past the rings to lubricate them and the cylinder walls/sides of the pistons. Some of that oil will make it to the piston tops. If the oil is very detergent, such as a HDEO, then it'll do it's cleaning action anywhere it gets!

 

[OMCWankel]

I agree Drew99GT. It has to be the detergents. Imagine the conditions the detergents have to deal with

My question is really directed at wheather the detergents action is different in the heat/pressure of the combustion chamber, as opposed to the nice, cosy, not as hot confines of the lubrication system.

 

[Quest]

Make sure that the HDEO oil you choose for your wankel engine is low-ash variety.

 

[Virtuoso]

I've never heard of an HDEO's combustion chamber cleaning ability; only it's ability to clean the interals of the engine.

If you want to clean your combustion chamber, grab some Techron.

 

[ebaker]

Because or the increased ash HDEO's should cause a slight increase in combustion chamber deposits.

 

[OMCWankel]

quote:

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Originally posted by ebaker:
Because or the increased ash HDEO's should cause a slight increase in combustion chamber deposits.

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Exactly! HDEO oils should cause a slight increase, if ash is the only factor. That HDEO oils cause a decrease in top ring groove deposits, a decrease in exhaust port deposits is a matter of record.

There must be a non-obvious mechanism involved here.

 

[bulwnkl]

The term HDEO can be misleading. It is used to mean an engine oil that carries the latest compression-ignition rating. In other words, the latest diesel engine rating. Presently, that rating is API's CI-4 Plus (aka CI-4+).

 

[kang]

Thanks, Bullwinkle. That’s a good definition. So what does this definition have to do with cleaning combustion chamber deposits? I don’t see the connection. When oil burns, it leaves lots of carbon deposits. I would think that even a high-detergent oil, if burned in the combustion chamber, would leave more deposits than the detergents would clean, for a net increase of deposits, not a net decrease.

 

[bulwnkl]

Yes, I agree. I think this is partly why many/most of the "all-fleet" (that's an oil with both compression-ignition and spark-ignition ratings. i.e. diesel and gasoline ratings) oil makers warn about possible increased sparkplug fouling when using an HDEO in gasoline engines. I am not in that business, so I cannot say for certain, but I believe the increased Detergent-Dispersant additive levels will get past the rings into the combustion chamber and possibly cause increased plug fouling. Having said that, it is certainly not guaranteed to happen. I have run LOTS of miles in lots of gas engines in lots of vehicles over the years using an all-fleet oil and have not had any noticeable ill effects from it.

 

[Solo2driver]

I was using Castrol Tection Extra HDEO in my 13B before switching to Royal Purple 15w-40 for the last 3K miles, no ill effects so far, plugs even look the same as when it was running Mobil DC 20w-50 for 50K miles.

BTW, engine has 200K miles on it, never been apart. I run Delvac in my wife's Saturn, other than lower fuel economy it seems to be slowly cleaning her engine up nicely.

-JamesW
DaveTurnerMotorsport.com

 

[OMCWankel]

Great to hear about your healthy 13B Solo2driver

Hope my RENESIS will make 200K miles someday.

Your experience is the same as others that have run HDEO in rotaries. Common wisdom is: the HDEO's will cause more carbon deposits, but your experience, and the experience of others indicates the reverse is true.

How does a higher ash oil not cause more deposits in the combustion chamber and exhaust port

 

[JohnBrowning]

Well I am not a big beliver in HDEO's ability to clean an already dirty engine! It will keep an already clean engine clean much better though. One of the tests for modern CI-4 HDEO is tha ability to keep the ring pack clean. PCMO does not have to pass this test and the test it does have to pass for ring and piston deposits is tame by comparison!

The mechanism by wich it does most of it's so called cleaning is that it leaves less of it's self behind so it creates less deposits. The second way is that it can hold more deposits in suspension so it will grab anything that wash's into the oil and hold it off of the parts. The third mechanism I belive is that the base stocks used for HDEO's have more natural solvency.

The down side to trying to clean an engine useing oil is that you are going to scarfice the oils lubricateing ability at an accelerated rate!

The best oils for cleaning are oils with high ester contents of 20% or greater. THe higher the ester content the better it cleans! Most high ester oils can do a major amount of cleaning and still turn in decent numbers!Ester based oils have an insane amount of natural solvency and can hold a beefier additive package.

 

[kang]

Excuse me for maybe asking the obvious. I had to look up HDEO (it’s not in the glossary on BITOG). From what I found, it stands for Heavy Duty Engine Oil. That seems pretty generic to me. You could have a whole bunch of different oils all calling themselves Heavy Duty when their formulations are completely different from each other. Exactly what makes an oil Heavy Duty? What oils (brands or weights) would NOT be Heavy Duty? Wouldn’t the cleaning mentioned above be a factor of the detergents and not “heavy” versus “light” duty? What is an example of a LDEO?

 

[OMCWankel]

Thanks for the reply John

So what you are saying, it is less about the solids left behind (ash), and more about solvents in the HDEO. This would imply that some of the HDEO is not consumed in the combustion process, and continues to clean on the way out the exhaust.

That makes perfect sense. I think you have the answer