Two technical oil questions (not covered by the oil threads)

[fireant911]

A couple of questions for the tribologists…

1.) Since motor oil is non-polar, it can be easily dissolved by other non-polar solvents (i.e., gasoline). If one’s automobile oil somehow became contaminated with gasoline, I am assuming that driving the car will do absolutely nothing to rid the motor oil of this contaminant? Is this indeed true? The reason for this question is that others have posted this 'driving procedure' as a fix for the removal of gas from motor oil and I cannot see how these miscible liquids could be separated by simply driving???

2.) The recommendation of changing one’s engine oil for a given mileage OR after a certain time has relapsed appears to be standard. The mileage decree I understand but what about the time statute? If motor oil was hydrophilic it would make sense – is this the reason? Contaminates are present in the oil by simply running the engine as well as the fact that certain acids are formed. Does this periodic ‘flushing’ of undesirable components entrained in the oil necessitate the time window for engine oil?

Respectfully and please, I am requesting facts and not opinions regarding these two questions.

[304065]

We know that when MFI cars dilute the oil with gasoline from frequent starts and short trips that don't boil it off, and then are operated at the track, the level in the tank can fall precipitously. We attribute this to the lighter components in the mixture boiling off.

The time limit is due to the acids formed by combustion, hence the annual recommendation, which is contained in the product literature.

[M.D. Holloway]

All the more reason not to flush a crankcase with a petroleum product (kerosene, diesel or even gasoline). The interesting thing is that the dynamic 'seal' that is created at the ring/cylinder liner interface does come in contact with fuel - in the vapor state. This film is constantly replaced. What happens in certain cases is that the fuel injection doesn’t happen at the right time and you can get fuel piston wash and oil blow-by.

All engine oils will easily mix with fuel - just the nature of the beast. The good thing is that the amount that is burned off is pretty small and the amount of fuel that does get dissolved by the oil is also small - unless there is a problem.

As for by-products occurring in the combustion process, true dat! Acids such as nitric, carboxylic and in some cases sulfuric occur. The other by-product that not many consider is water. Water is a by-product of the combustion cycle. Good engine oil will be able to neutralize those acids - look at the TBN of the oil. Normally the higher the better - say above 11 or 12.

[M.D. Holloway]

I looked at your questions again. The fact is, normal operation will not get rid of any fuel that finds its way into the oil infact it will help the oil breakdown quicker to form deposits. Fuel in the oil is never going to burn off. Secondly, changing the oil is one way to rid your crank of junk provided the oil is still working at dispersing nasties. Some oils lose this talent. The question is, where are these things coming from? Well, stuff gets in oil only one of two ways - internally or externally. Externally, contames get in by 1) Implantation (from the dirty OEM), 2) Ingested (breathed in threw the filter or dip stick), 3) Induced (from poor maint prax). Internally by 4) Generated (wear particles, oxidation products), 5) Escaped (from the filter).
If you look to thwart the influx or generation of these nasties then it would follow suit that the oil and engine will last longer - and it does. I have mounds of evidence to support such.

[fireant911]

Mike,
Many thanks for clearing up these issues for me!!!

[M.D. Holloway]

no probs - anytime

[dshepp806]

Good take, LubeMaster.

Best,

Doyle

[RWebb]

Originally Posted by LubeMaster77

...normal operation will not get rid of any fuel that finds its way into the oil infact it will help the oil breakdown quicker to form deposits. Fuel in the oil is never going to burn off. ...

what makes you say that gasoline will never volatilize off?

[M.D. Holloway]

Kinetics - the temp it takes to flash is above the reaction temp for the oil and fuel. You actually don't have to be very hot to get some things to occur. On the lab bench the Rx works out really well. I can make a really nice sludge pretty quick by bringing oil up to operating temp with a few drops off gas in it. In an engine the situation is far worse. It is contained and you also have shearing pressures. Add a little yellow metal or some water (which is common in engines) and you really get a show. I have done it many a time during seminars to show how oils deal with heat and fuel and metals and water. It is pretty dramatic and often duplicated in R&D labs when trying to develop the next best formula.

[M.D. Holloway]

something else I found concerning fuel in oil...

Fuel Dilution
Frequent starts of an engine, excessive idling and cold running conditions can lead to moderate fuel dilution problems. Severe dilution (excess of two percent) is associated with leakage, fuel injector problems and impaired combustion efficiency. These are symptomatic of serious conditions that cannot be corrected by an oil change. According to one reference, 0.36 percent of total fuel consumption ends up in the crankcase. Problems associated with fuel dilution include:
• Fuel dilution in cold operating conditions can cause waxing. During startup, this can result in low oil pressure and starvation conditions.
• Fuel carries unsaturated aromatic molecules into the motor oil which are pro-oxidants. This can result in a premature loss of base number (loss of corrosion protection) and oxidative thickening of the motor oil, causing deposits and mild starvation.
• Fuel dilution can drop the viscosity of a motor oil from say, a 15W40 to a 5W20. This collapses critical oil film thicknesses, resulting in premature combustion zone wear (piston, rings and liner) and crankcase bearing wear.
• Fuel dilution from defective injectors commonly causes wash-down of oil on cylinder liners which accelerates ring, piston and cylinder wear. It also causes high blow-by conditions and increased oil consumption (reverse blow-by).
• Severe fuel dilution dilutes the concentration of oil additives and hence, diluting their effectiveness.
• For Diesel Fuel dilution by biodiesel may result in higher than normal problems compared to diesel refined by crude stock. These problems include oxidation stability, filter plugging issues, deposit formation and volatility resulting in crankcase accumulations.

[MBruns]

The bigger broblem if it makes it that far is washing down the cyls. or killing the rod bearings !

Mike Bruns JBRacing.com

[rnln]

How about seafoam or B12 thing? Will they have the same problem when adding into engine oil?

Originally Posted by LubeMaster77

All the more reason not to flush a crankcase with a petroleum product (kerosene, diesel or even gasoline). The interesting thing is that the dynamic 'seal' that is created at the ring/cylinder liner interface does come in contact with fuel - in the vapor state. This film is constantly replaced. What happens in certain cases is that the fuel injection doesn’t happen at the right time and you can get fuel piston wash and oil blow-by.

All engine oils will easily mix with fuel - just the nature of the beast. The good thing is that the amount that is burned off is pretty small and the amount of fuel that does get dissolved by the oil is also small - unless there is a problem.

As for by-products occurring in the combustion process, true dat! Acids such as nitric, carboxylic and in some cases sulfuric occur. The other by-product that not many consider is water. Water is a by-product of the combustion cycle. Good engine oil will be able to neutralize those acids - look at the TBN of the oil. Normally the higher the better - say above 11 or 12.

[M.D. Holloway]

the molecular weight of the flushing product has to be taken into consideration - light distillates will cause all sorts of issues where larger molecules that are typically higher distillates will be better

[RWebb]

Originally Posted by LubeMaster77

Kinetics - the temp it takes to flash is above the reaction temp for the oil and fuel.

one problem - the flash temp. is the wrong one to use; [another common problem is that people think about the boiling point - also not correct]

the gas fraction will begin volitalizing off even at room temperature -- easy to see in action: put a pan of water in your room -- it will volitalize (evaporate) even tho it is far cooler than 212 oF - and of course has no flash pt. -- even ice will sublime away [e.g. on glaciers - creating neves pennitente which make it tough to travel on glaciers]

as a practical matter you might be right -- if the [catalyzed] rxn with the hot oil proceeds much faster than the volatlization....

it sounds like those with much gas in their oil should change it -- not sure how much tho -- e.g. what if their mfi 'dribbles' 8 drops a week? 8 a month?

[RWebb]

just a sep. post to highlight the problem mike noted with EXCESSIVE IDLING re fuel dilution [above]

maybe some of the people who persist in thinking a long time idling is good will see this....

[M.D. Holloway]

Fuel Lowers the FP of oil and oil raises the FP of fuel - depending on the concentrations. Flash point of the oil is a better way to quantify percentages of fuel contamination. This test measures the temperature at which the oil will ignite when an open flame is applied to it. Since diesel fuel typically flashes at approximately 130 F° (gas is lower) and engine oil flashes at approximately 420 F° , the amount of fuel can be estimated by the decrease in used oil flash as compared to new. One caution advised when using this method to determine percent fuel dilution is that excessive antifreeze contamination will also reduce flash point. Therefore, if antifreeze contamination is indicated, flash point cannot be relied upon to accurately measure fuel percentages.

The most accurate method for a quantitative measurement of fuel dilution is gas chromatography. This is a method of separating the contents of the sample by boiling point. The accuracy of this method is 0.1% and is normally repeatable to the nearest 0.5%.

[M.D. Holloway]

I know from college chemistry that if you have a R-H and hit it with energy such as heat then you get R`, take that and introduce O2 and you get R-O-O`. The further reaction to produce a peroxide occurs when you take the R-O-O` and combine it with R-H to get the R-O-O-H + R`. (the carboxylic acid with the radical). The R in this case runs real fast if it is a small molecule like fuel. It chops the sheet out of bigger molecules weak links.

Fuel is never good in engine oil...

[M.D. Holloway]

Think about it even further - why? Cuz I have no life! The problem with fuel in the oil is that lots of other reactions also occur, and the products of these other reactions (there are potentially hundreds of them) can be the reactants of other reactions that may are may not be radical driven. And under the extreme conditions of combustion, not all free radical reactions will proceed by first forming a peroxy radical (especially if oxygen is limited). You also have the additives (both from the fuel and the lube oil) that can have significant effects on hundreds of reaction pathways, not just by free radical mechanisms but by ionic mechanisms. The now well known problem of using large concentrations dimer acid corrosion inhibitors in fuel (for lubricity improvement) and their adverse effect of crankcase oil filter plugging is a good example of an important reaction mechanism that in no way involved any free radical formation.

It is a lot more complex than even most of the scientific community in this area thought it was. For instance, the tendency of biodiesel to form insolubles in lab bench tests may not always track with their tendency to form deposits on hot metal surfaces (such as fuel injectors in the "fuel part" of the engines or piston rings on in the "lube oil part" of the engine. Kinda throws a monkey wrench into the biodiesel objections. This is still a hot arguement amongst us geeks!

It becomes even more complex when you mix that biodiesel into a blend that contains the entire milieu of compounds present in a heavy duty diesel motor oil. Now add to all that the effect of the soot being formed and the active sites on the surface of that soot that may adsorb certain compounds (or not), the effect of the change in the surface properties of the soot as materials adsorb. In addition, the hot metal surfaces can and likely do act as a heterogeneous catalyst to some (but not all) reactions. Also remember that the vast majority of individual chemical reactions that occur in the fuel and/or lube oil do not manifest themselves in the form of insolubles or other solids that form deposits on metal surfaces.

You could take the biodiesel model and interchange it with gas and come up with the same issues. Your engine is a powerplant and a chemical reactor - it would be cool to take advantage of that.

hmmmm....

[vytenis]

So are we saying that once fuel and or water are mixed with the oil, that running the car with an oil temp. in the 200-250 degree range won't remove water/fuel from the oil? Doesn't sound right.

"V"

[M.D. Holloway]

its true - I can show you countless examples of oil analysis results where fuel is found in the sample then if left in, it doesn't leave. Sad but true...