dino vs. synthetic HDEO "cleaning" properties

[1sttruck]

I think it's primarily the detergents that do the cleaning, judging from the 'ashless dispersant' aircraft oils. From what I understand they haven't used detergents in aircraft oils since the 50s or so, as you don't want an oil dislodging a big plug of sludge and clogging an oil line when you're at 20k feet, but you don't want sludge to build either so they try to keep it suspended. Base stock and such differences seems like it might do some cleaning, as when sludge and varnish form it's by definition not soluable in that oil, but when using a synthetic after dino has been used there seems to be some cleaning. It's also interesting that they don't use 100% synthetic oil in piston engined aircraft as they found that they needed to add quite a bit of dino to get the cleaning/lead removal that they needed, and ended up with a blend that was essentially no different than existing blends. HDEOs will have more aggressive cleaning than PCMOs, some say too much as there is competition at metal sites for detergents, moly friction reduction additives (they don't seem to reduce wear) and anti-wear additives, but judging from the junk that people find in their filters even after exclusive Mobil 1 PCMO use I don't think that there is too much. Diesels seem to usually do fine with engine life.

I like using synthetic/dino blends anyway for cost reasons, using 2 qts Mobil 1 T&S with 3 qts of Mobil 10W-30 in both cars, and 1 gal of Mobil 1 T&S with 2 gal of Delvac 1300 in the truck. Maybe I've ended up with optimum cleaning by accident.

 

[1sttruck]

Forgot to add 'after using autorx,' after 'find in their filters'.

 

[427Z06]

I believe that you'll see a very limited additional cleaning affect when switching from a "low" detergent dino (PCMO) to a "high" detergent dino (HDEO). However, when you switch basestocks you might see a bigger affect. For example, take a high mileage engine that was run on inexpensive dinos (PCMOs) for the "normal" factory intervals, then switch to a synthetic with a high Ester or AN content, I think you may then see a substantial cleaning affect.

 

[ToyotaNSaturn]

Wayne, the difference in cleaning between the two oils you mention is too close to call. Probably no discernable difference...

 

[wavinwayne]

Would the engine "cleaning" properties of a dino HDEO (Shell Rotella 15w40) be the same as a synthetic HDEO (Shell Rotella T 5w40)?

 

[Cyprs]

If the TBN of both oils are the same as are XD3 15-40 dino & XD3 0-40 syn then can one deduct they should be similar? My understanding TBN plays part in keeping engine clean.

That is a good question.

Cyprs

 

[TooSlick]

The cleaning effect you see from some synthetic lubes comes primarily from the solvency of their ester components. This is why not all synthetics seem to clean as effectively....

Detergent additives are helpful in preventing deposits,however they do little to clean up pre-existing ones. There would be some marginal cleaning effect from using a petroleum diesel oil; compared to a low TBN, gas engine oil....

TS

 

[wavinwayne]

quote:

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Originally posted by ToyotaNSaturn:
Wayne, the difference in cleaning between the two oils you mention is too close to call. Probably no discernable difference...

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Thank you

 

[JohnBrowning]

I was going to say much the same thing as TooSlick!

 

[widman]

Depending on the ester content, you might get more cleaning. Some cleaning actually does happen with good high detergent dino oils. I've actually taken most of the sludge out of a pickup with weekly changes of a 3300 ppm calcium 10W-30. No, it will never be as clean as new without an autoRX treatment, but it cleaned up a lot.
Oils in small aircraft are only in there for 25 hours, so I'm guessing there isn't much time for sludge to form. UOA shows lost of silicon contamination and wear metals (and high lead from the leaded gasoline).

 

[DJ]

Switching from a couple fills of Amsoil(and nothing steadily before that switched brands all the time some synthetic and dino) to the Rotella 5w-40 my car absolutely experianced cleaning. Within a couple hundred miles the engine became louder a filter swap quieted it right back down, the first two fills became black fairly quickly as well. I am not saying Amsoil sludged up in the engine I am just saying the Rotella was cleaning up stuff the Amsoil had not.

 

[AV8R]

The dispersants in aviation engine oils and gas and diesel oils are there to keep particles in the oil from coalescing and collecting on engine surfaces, and they are active at fairly low temperatures. The detergents activate at higher temperatures in the ring belt and exhaust valve areas. They do minimize hard, high-temperature deposits, but do not have much to do with cleaning areas of the engine much cooler than the exhaust valve stems (for example, the intake stems are normally too cool for the detergents to activate). The dispersants and natural solvency of the base stocks do the cleaning.