Is the effect of fuel dilution permanent?

[mechanicx]

There is an interesting thread in an obscure part of these forums, I think in the oil science forum.

Fuel dilution

That thread got me wondering about fuel dilution. My thinking is that fuel acts as a solvent in oil so it dilutes oil more than just the combining of a lower visosity fuel with the oil. For lack of a better term I was thinking that fuel disperse or breaks up the oil chains like I assume a solvent does.

This lead me to another question tied into whether fuel dilution is just the sum of viscosities or if it is also has a greater diluting/solvent effect.

If you have fuel dilution and lowered oil viscosity and you fix the cause of the fuel dilution, after the fuel evaporates out does your oil viscosity return to normal?

 

[Quattro Pete]

IIRC, the effect is permanent, meaning the damage to the oil was done, so removing the fuel won't bring the oil back to normal. This was discussed here recently, but I don't have the link handy...

EDIT: here is the link:
https://bobistheoilguy.com/forums/threads/fuel-dilution-quandry.119176/

 

[Bryanccfshr]

Gasoline can dislolve plastics or old style VII's Those won't heal when broken apart. Some oils use advanced PAO's and esters as VII's and I don't know how succeptable they are to breakdown when exposed to solvent.

 

[mechanicx]

OK thanks, I'll have to read that. I guess nothing or any idea is new under the Sun or on BITOG lol.

 

[mechanicx]

Originally Posted By: Bryanccfshr
Gasoline can dislolve plastics or old style VII's Those won't heal when broken apart. Some oils use advanced PAO's and esters as VII's and I don't know how succeptable they are to breakdown when exposed to solvent.


So the fuel breaks down the VII more than the oil itself? So the lowered oil viscosity from fuel dilution primarily shows up at 100Cand not so much at low temperatures?

 

[Quattro Pete]

No problem. FYI, I didn't mean to extinguish the discussion by referencing a previous thread. Same subjects can be discussed multiple times, and additional info can be posted each time, so it's all beneficial.

 

[mechanicx]

Yeah I just finishing reading that thread. It answered the basic question but was short and not much details. An in-depth discussion and breaking fuel dilution down into the tiniest minution would be good too

.

It now makes me wonder just how much viscosity drop that we see is really just shearing or from cold starts and the fuel evaporated away and leaving the oil visosity drop behind.

 

[PT1]

What brand/viscosity oil is most resistant to fuel dilution?

 

[mechanicx]

PP j/k! That is a good question. I like Quaker State Conventional but I had an UOA that showed fuel dilution and the 5W30 viscosity dropped to 8.2 within 2800 mi. That sounds like a lot.

If fuel dilution is mostly a matter of VII being disolved, you got to assume a straight weight is tops followed by any synthetics with a very "tight" viscosity spread.

 

[Ben99GT]

Redline says their oils can be heated to burn off excess fuel and reused, excess fuel dilution as seen in Top Fuel.

 

[mechanicx]

Yeah but I'm not running nitromethane

. But seriously I imagine Redline does well with any fuel dilution. I wished I understood gasoline's effect on oil viscosity better.

 

[GMorg]

Below is a link to the last time that I recall this being discussed with depth.

http://www.bobistheoilguy.com/forums/ubb...true#Post680042

 

[labman]

40 years ago I worked for Rinshed Mason, a major supplier of the acrylic top coat that GM used at the time. Part of the process was to take powdered cellulose acetate butyrate and dissolve it in solvents. We also prepared acrylic resins in solvents and blended them along with plasticizers. The final product was sprayed on the cars and the solvent boiled off in an oven leaving the film of polymers. That is a very common process. Some plastic film is even prepared that way. Enamels are much the same except they cross link also as they dry. So dissolving a polymer in a solvent no way degrades it.

Elastomers such as rubber are different. They don't dissolve, but swell. The swelling can break the crosslinks degrading the material.

So gasoline should work like like a very thin basestock thinning the oil out. A good highway run should boil the gas off returning the original viscosity. I have seen enough of the real world to know things don't always work the way they should.

 

[mechanicx]

That was kind of interesting, thanks. It was kind of confusing though and didn't seem to stick to the topic of fuel dilution.

You seem to be of the position that fuel dilution is mostly the sum of viscosities and not that big of an issue, right? I think that fuel has a "solvent" effect and breaks down the oil, maybe the VIIs. I know coolant in the oil is damaging and can cause engine failure, but is fuel dilution not as damaging?

 

[mechanicx]

So you seem to be suggesting the fuel only temporarily dilutes oil and doesn't break it down. I'm confused now

.

 

[fdcg27]

RLI!

 

[labman]

I think coolant can lead to rusting of iron and perhaps corroding other metals. Gasoline won't.

By the way, it is actually the product of the viscosities, at least with solvents and polymers. At least that is the way I remember it a long time ago.

 

[GMorg]

I think that we have to keep in mind that the gasoline has additives too. And, gasoline would seem easier to oxidize. So, I would think that fuel in the oil would exhaust some of the oil additives (permanent) and would compete for metal surfaces producing elevated wear (permanent) and slightly descrease viscosity (temporary). I could also see fuel disrupting some of the multifunctional additives that circulate as micelles. Given enough time, I would think that this would be temporary.

I suggest that we should think of organic solvents as any other solvent. They are not harsh in the sense that they are destructive. If you use water as a solvent to dissolve starch and salt, you could add a little alcohol and neither of the solutes would fall out of solution or be harmed in any way. When the alcohol finally evaporated, the solution would return to its original state. When the water evaporated, the salt and sugar would return the their original state. Nothing would be destroyed.

On the other hand if you added too much alcohol, the starch would begin to precipitate. After the alcohol evaporated, the starch would return to solution. Nothing changed in the long run, but temporarily the starch would be very different than when it was in solution.

 

[Bryanccfshr]

Keep in mind that standard VII act on mechanical action and not chemical action. They are coils that expand and physicaly increase in size as the temperature increases resulting in the oil thinning less than it would without those coils. A solvent can cause them apart, the polymers are still chemically the same but they can be "broken" from solvent action, either breaking them physically apart from solvent action on existing fractures in the physical coil or perhaps chemically reacting with them and reducing their ability to expand in heat and reducing the VII function of the polymer.

Redline as far as I understand avoids or minimizes polymers and uses more inert components to provide this function including basestocks that meet the viscosity index needs and are less succeptible to breakdown from fuel dilution.

I think that synthetic oils including grp III's types have an advantage in this type of abuse(fuel dilution) because the base oils natural VI reduces the amount of VII's needed to meet the task.

Polymers have been shown to be reactive and a first failure component of engine oil and are blamed for deposits in wide Viscosity span oils.

They are not the only evil in fuel dilution, it is best of course to avoid fuel dilution if at all possible becasue it is not beneficial for any of the engine oil components or the synergy of any formulation.

My limited knowledge on the topic would indicate that Polymetric VII's are the weak link in modern engine oil formulation.

 

[mechanicx]

Yeah that seems right and to be the consensus that fuel can permanently lower the oil viscosity and acts like a solvent on the VII. I think you alluded to a good point and I bet a big part of what lead to sludging with the early multi-viscosity oils was carburetors running rich and diluting and oxidizing the oil and maybe the VII became damaged and sludged even more.