Oil viscosity vs. gasoline dilution

[StromRider]

Is there a formula that can determine what the effect of a given percentage of gasoline dilution would have on an oil with a known weight? For instance if my used oil analysis on originally 14 cSt oil says I have 1.5% dilution and a viscosity of 10 cSt can I figure out how much viscosity was lost to shearing and how much was from the fuel?

 

[BobFout]

Flash point would give some clue. Also, what engine?

 

[GMorg]

It seems that gasoline has a viscosity of between .4 and .7 cSt at 100 C. Even if the viscosity was zero, at 1% dilution, the maximum that fuel dilution could reduce viscosity would be about 1%. The reduction that you are seeing is essentially all due to shearing.

Reference for viscosity:
http://www.engineeringtoolbox.com/kinematic-viscosity-d_397.html

 

[mechanicx]

This is interesting. I had a recent UOA done and the 5W30 had sheared down to 8.2 and there was >5% fuel dilution. I'm not really so sure about the accuracy of the test results. I'm a little unknowledgable on the subject but wouldn't more than just the viscosity of the dilution matter? If gasoline acts as a solvent wouldn't that break down the oil and lower its viscosity independent of just diluting it?

 

[StromRider]

Originally Posted By: mechanicx
This is interesting. I had a recent UOA done and the 5W30 had sheared down to 8.2 and there was >5% fuel dilution. I'm not really so sure about the accuracy of the test results. I'm a little unknowledgable on the subject but wouldn't more than just the viscosity of the dilution matter? If gasoline acts as a solvent wouldn't that break down the oil and lower its viscosity independent of just diluting it?


I also wonder if the addition of fluids with different viscosity will really add together in a nice linear fashion. I am hoping Bruce or Molecule will chime in here at some point.

 

[mechanicx]

Yeah I think this thread should be moved to the PCMO forum and then we'd get more feedback.