Diesel In Engine Oil Test

[90cummins]

I have used the blotter test with white 3x5 index cards to check for excessive soot content in our test cell diesels and my own vehicles. Paper towels are too porous to illustrate any differences in viscosity.
Placing several drops of oil in the middle of the card and setting it aside for a couple hours or days in a warm environment will allow the oil to slowly be absorbed leaving the insoluble’s behind. Excessive soot will show up as a shiny spot in the middle of the test area.
Fuel dilution may work with 3x5’s because they are thicker and more dense thus slowing the absorption rate. I would think testing for fuel dilution would be a timed event.
As with any method you need to have multiple samples & data to determine what is excessive.

90cummins

 

[fluttersmith]

OK, thanks for the comments. To address concerns about temperature, I repeated the 0 and 30% diesel tests at 150 Deg F (attached). Again no difference in the samples with and without diesel. Others may have a point about used oil, "soot loaded" - perhaps there is a chemical presence in well-used motor oil that will produce a real difference with diesel. Another test?

 

[BGigHarbor]

OK, thanks for the comments. To address concerns about temperature, I repeated the 0 and 30% diesel tests at 150 Deg F (attached). Again no difference in the samples with and without diesel. Others may have a point about used oil, "soot loaded" - perhaps there is a chemical presence in well-used motor oil that will produce a real difference with diesel. Another test?
View attachment 344629

How about on some tissue paper?