Fuel Dilution - Efect on Viscosity Index Improvers / Modifiers

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Is there any info that you guys know of regarding gasoline's effect on viscosity index improvers, mainly OCP?
I read a thread in here where someone mentioned that at one point Dyson said that fuel dilution decomposed them,
but I couldn't find the source of this info.

This is not a question regarding the effect fuel dilution has on a blend's viscosity.
 
Yes.

"Originally Posted by buster
I have a question. Do viscosity modifiers break down when there is fuel dilution? The reason I'm asking is I've noticed over the years that Redline rarely drops a a a grade even when there is fuel dilution and it appears that oils with a larger spread, which often indicates more VII, tend to lose a greater percentage of their viscosity than those with a narrow spread. Is this due to the concentration of viscosity modifiers? Thank you

Gokhan
"That's correct! This is the reason why only monograde oils are specified for two-stroke-cycle diesel engines. VII and fuel dilution do not mix.

However, the reason is not because the VII breaks down with fuel dilution. VII amplifies the viscosity at all (operating) temperatures by the same constant. In other words, KV is multiplied by the same constant at 40 C and 100 C. When there is fuel dilution, the base oil viscosity is reduced and this multiplication constant amplifies the effect"

This has been my observation. Redline uses thicker baseoiks with little VII's and rarely loses its viscosity."


See this post on VII's. Last page.

https://www.bobistheoilguy.com/foru...-index-improvers-are-not-bad#Post5108589
 
Originally Posted by Gokhan

"That's correct! This is the reason why only monograde oils are specified for two-stroke-cycle diesel engines. VII and fuel dilution do not mix.


I heard the reason was for metallurgical differences. I don't think I have ever seen fuel dilution in ANY DD 2-stroke.

LOTS and LOTS of soot, though -- that's another story!!
 
I don't think Dyson used the term correctly.

Chemical decomposition usually refers to the breakdown of a chemical substance into its constituent parts or elements.

OCP VII's are the joined polymers of Ethylene and Propylene, hence Olefin "Co-Polymers." I haven't seen any scientific papers that show that fuel dilution breaks down that polymer structure.

OCP VII's can be constructed such that various other compounds can be grafted onto the backbone structure to provide increased stability and extra functionality. By functionality we mean that VII's can also be constructed to provide functions other than just viscosity modification.

I would be more concerned with the overall reduction in bulk viscosity of the oil as the bulk viscosity determines oil film thickness (OFT)

Here is a good presentation covering most if not all aspects of engine oils

Technology of Engine Oils
 
Last edited:
Originally Posted by Linctex
Originally Posted by Gokhan

"That's correct! This is the reason why only monograde oils are specified for two-stroke-cycle diesel engines. VII and fuel dilution do not mix.


I heard the reason was for metallurgical differences. I don't think I have ever seen fuel dilution in ANY DD 2-stroke.

LOTS and LOTS of soot, though -- that's another story!!

Two cycle Detroits required straight 40 grade because multi grades (15w-40) slipped past the oil rings too easily and gushed out the air box drains. A good running Detroit created less soot than the 855 Cummins. But you could always guess a Mack on the freeway with the black smoke rolling out the stack. If a Detroit had fuel dilution it would run away (uncontrolled engine speed until the "bang").
 
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