boil-off phase for fresh oil?

[zach1900]

I know Ford and Conoco did a study on this years ago, basically changing oil to often always kept the engine in boil off phase, I never really understood the mechanism to this , were these old oils that were more prone to initial shearing or were/are they the additives like Zinc?

 

[KCJeep]

I don't know what you mean by boil off phase?

New oil will strip off the old oil and lay down it's own new protection layer. This takes 1000 to 1500 miles to completely occur IIRC. Wear goes down after that, all the way to the point the oil is breaking down and protection begins to lag again (this is quite a while with todays modern lubes, even conventional).

So changing too often keeps you in the higher wear transition phase much more of the time. Is that what you are asking?

 

[4wheeldog]

"Boil off" sounds to me like a reference to NOACK. Some conventional oils may boil off some lighter elements in initial use, but a synthetic should be considerably more stable, with NOACK being more or less consistent, through a normal OCI.

 

[zach1900]

Originally Posted By: KCJeep
I don't know what you mean by boil off phase?

New oil will strip off the old oil and lay down it's own new protection layer. This takes 1000 to 1500 miles to completely occur IIRC. Wear goes down after that, all the way to the point the oil is breaking down and protection begins to lag again (this is quite a while with todays modern lubes, even conventional).

So changing too often keeps you in the higher wear transition phase much more of the time. Is that what you are asking?
that's exactly what I was trying to say.

 

[MolaKule]

Originally Posted By: zach1900
I know Ford and Conoco did a study on this years ago, basically changing oil to[o] often always kept the engine in boil off phase, I never really understood the mechanism to this, were these old oils that were more prone to initial shearing or were/are they the additives like Zinc?


Volativity is the evaporation of the lighter hydrocarbon molecules in mineral oils.

There is nothing wrong with changing oil early except for the cost.

 

[Shannow]

http://www.bobistheoilguy.com/forums/ubb...e_a#Post3372187

Ring belt temperature residence and transport time are discussed.

There's a school of thought on BITOG that Noack is meaningless in engines as the sump never sees 250C...whereas as per the paper linked the oil can spend many tens of seconds at those temperatures on the path through the rings and back.

Think of a mini distillation process up there.

Do I THINK there's be a difference between a 7-8% Noack changed at 7,000 miles versus a 12-13% Noack changed at 3,000 miles ?

Gut feel is that the latter is a worse situation...but that's all I'll posit.

 

[bbhero]

Hmmm... I've actually pondered this has well. I'm sure the Noack does matter because they wouldn't test it if it didn't. And hydrocarbons that evaporate off have to have a deleterious effect to some effect. Form deposits somewhere.. Like the piston rings?? I am hypothesizing this..

 

[Garak]

Originally Posted By: Shannow
Do I THINK there's be a difference between a 7-8% Noack changed at 7,000 miles versus a 12-13% Noack changed at 3,000 miles ?

Gut feel is that the latter is a worse situation...but that's all I'll posit.

For deposits, it might matter, but for consumption, it certainly didn't. There were taxis that didn't burn oil in the day, despite the high Noack oils of the day and 10,000 km OCIs.

 

[pitzel]

I'll give you a bit of a nerdy explanation from back when I was a Chem Eng student. In Chemistry, there is what is known as the 'activation energy' for a reaction, and it basically follows a statistical distribution described by the Arrhenius equation and the Boltzmann distribution.

Basically put, in the oil refiner's vacuum distillation tower, virgin motor oil only sits in there for, at best, a relative short period of time as it is being processed into base stocks through fractional distillation. What comes out of the particular fraction drawn as a given base stock is a homogenous mixture of various chain length hydrocarbons (ie: paraffins) with the statistical distribution centered around what is desired for a particular fraction. This is used as basestock and blended with various additives and sold as retail motor oil.

When oil is poured into an engine and boiled for an additional few dozen hours, more of the lighter fractions in that overall 'distribution' of paraffins that end up in a bottle of retail motor oil boil off. This is where the mass loss comes from as oil is in service. The boil off heavily goes into the PCV system (which exerts a slight vacuum on the crankcase) and ends up in the intake system where, in a DI engine, it can deposit on valves and other intake components. As well as other instrumentation/actuators in the overall combustion gas path.

Automakers, on account of moving to DI, have imposed some pretty extreme specs in terms of volatility (as measured by NOACK) on the lube industry to protect the intakes. In DI engines, changing oil more frequently than recommended by the manufacturer can actually cause a whole host of problems. Those who advocate more frequent oil changes in DI engine cars are actually doing their owners a giant disservice as without fuel (with weak diluent/solvent properties) being inducted into the intake, there is literally no way to deal with the deposits that inevitably will result from such. Eventually intake port occlusion, or potentially even worse damage if the deposits are somehow liberated from the intake will occur. I'd have to disagree strongly with MolaKule on his comment about changing oil more frequently not causing harm.

 

[HangFire]

Interesting.

But wouldn't the fuel contamination quickly reappear in the fresh oil? I guess the answer depends on the rate of contamination versus the rate of boil-off/evaporation, which may be situation dependent.