What causes varnish to begin building up?

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Just paid (through work) for an undergrad thesis into turbine oil varnishing, and it's pretty irrelevant of fuel dilution...it occurs in systems which have absolutely no contact with fuel.

It's oxidation, localised or systemic heat...moisture and dissimilar metals help it. Localised can be through diesling due to aeration, tight clearances on a dodgy bearing, spark discharges etc. etc.
 
Originally Posted By: tig1
TomNJ might have a tech answer for you, but I believe base stock and OCI may have a lot to do with it. All I know is that my engines don't have varnish problems even with 200K+. Both Duratechs are clean as new from what I can see through the oil fill hole. I have pics if you want to see them.


Hey tig1 rather than devolving responsibility to Tom NJ to provide an answer (technical or otherwise), I feel it would be just as valid if you gave specific details about your maintenance routine etc and what you believe keeps your engine varnish free.

The link to how clean an engine may also provide a clue.
http://www.bobistheoilguy.com/forums/ubb...rue#Post2486312
 
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Originally Posted By: Pablo
In automotive applications, unburned fuel trumps the others.


Through which process ???
 
Originally Posted By: Shannow
Originally Posted By: Pablo
In automotive applications, unburned fuel trumps the others.


Through which process ???


Attack on the oil components (dyes and non-ester additive carriers) via oxidation and direct deposition.
 
Originally Posted By: Shannow
How does fuel oxidise these components ?

What about oxidation of the base-stock ?



Heat, free radicals, acids, messy organic chemistry.

It happens but most decent base oils are a bit more resistant.
 
OK, fuel is extracted from crude.
Basestocks are extracted from crude (give or take)...

How does hydrocarbon/hydrocarbon interactions create "messy organic chemistry" ?
 
Like I said, it's an oxidative process.

And it's one that feeds upon itself in ideal conditions for varnish...whether unburned fuel is present or not.

Oxidation is the issue, not fuel, burned or unburned.
 
Originally Posted By: Shannow
Like I said, it's an oxidative process.

And it's one that feeds upon itself in ideal conditions for varnish...whether unburned fuel is present or not.

Oxidation is the issue, not fuel, burned or unburned.


I guess chicken or egg, but after doing this for 35 years, and talking with lots of folks in the piston driven engine lube world - in all spectra. Take a tight engine, take a "loose" engine (simple terms for one car that has plenty of blow by) - the car with lots of partially burned and unburned raw fuel - all other conditions the same, guess which engine will way, way, way more rapidly have varnish and nasty build up?
 
Originally Posted By: LeakySeals
HEAT


Yep, heat, time, and aluminum used in the construction of some engines seems to hold it more than iron did. Running an oil too long doesn't help either. JMO
 
Originally Posted By: Pablo
Originally Posted By: Shannow
Like I said, it's an oxidative process.

And it's one that feeds upon itself in ideal conditions for varnish...whether unburned fuel is present or not.

Oxidation is the issue, not fuel, burned or unburned.


I guess chicken or egg, but after doing this for 35 years, and talking with lots of folks in the piston driven engine lube world - in all spectra. Take a tight engine, take a "loose" engine (simple terms for one car that has plenty of blow by) - the car with lots of partially burned and unburned raw fuel - all other conditions the same, guess which engine will way, way, way more rapidly have varnish and nasty build up?


I like talking to people too.

I get paid for doing stuff 'though.
 
Originally Posted By: Shannow


I like talking to people too.

I get paid for doing stuff 'though.


I thought we were having a civil discussion why did you whip that one out? Last time I checked I "do stuff" all day long and have a business that I "do stuff" at night and neither involve Amsoil. Plus, I'm not sure how much of your stuff involves working with real lube and engine experts. Plus saying that junk does not discredit what I wrote. I thought you were a tad above the personal junk.
 
Originally Posted By: Pablo
but after doing this for 35 years, and talking with lots of folks in the piston driven engine lube world - in all spectra. .
.
.
. way, way, way more rapidly have varnish and nasty build up?


Guess I took it over the top at that point hey Pablo ?

???
 
Let's just leave it at this: Gasoline piston engines with lots of combustion blow-by will have rapid varnish build up via the oil breakdown and the partially combusted fuel itself.
 
Originally Posted By: Pablo
Originally Posted By: Shannow
Like I said, it's an oxidative process.

And it's one that feeds upon itself in ideal conditions for varnish...whether unburned fuel is present or not.

Oxidation is the issue, not fuel, burned or unburned.


I guess chicken or egg, but after doing this for 35 years, and talking with lots of folks in the piston driven engine lube world - in all spectra. Take a tight engine, take a "loose" engine (simple terms for one car that has plenty of blow by) - the car with lots of partially burned and unburned raw fuel - all other conditions the same, guess which engine will way, way, way more rapidly have varnish and nasty build up?


hmmm.... I never had fuel in either of my V70's, the NA or the turbo, but as you know that engine is prone to varnish on the top end. A quick look at the UOA's posted on here seem to show very little fuel dilution as well? I always assumed it was due to heat and oil routing. Cars with timing chains seem to do a little better in some cases, maybe because of the oiling requirements and the splash lubrication provided by the chain itself? Just a guess.
 
Varnish formation is the result of oxidation. One of the key components of oxidation is heat. Heat induced oxidation can be accelerated by unburnt fuel and especially nitrogen compounds present in partially burnt fuel.

Pablo and Shannow are arguing about the same thing. Shannow about the chemical reaction and Pablo about contributing factors.
 
Originally Posted By: OldCowboy
Varnish formation is the result of oxidation. One of the key components of oxidation is heat. Heat induced oxidation can be accelerated by unburnt fuel and especially nitrogen compounds present in partially burnt fuel.

Pablo and Shannow are arguing about the same thing. Shannow about the chemical reaction and Pablo about contributing factors.


Kinda sorta. Agree about the same thing!
 
Informative, but what about the in between stuff?

E.g., I have varnish in my top deck along with the barnacled hard crusties or carbon. I didn't have any typical sludge, btw.

The heat coked something on the valve train.

So, I wonder what is the chemical dymanic here?
 
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