Cardboard test for fuel dilution

[Treyes1]

Hi all,

Did an oil change on an Audi 3.0 Supercharged V6 with 122k miles. The oil was changed after 3000 miles, but about a liter of oil was added half way through the OCI (repaired two oil leaks that one of the repairs involved losing .5 liter)

The oil had a slight fuel smell that was discernible. Admittedly, it was very subtle and not a pungent smell. The smell was confirmed by a fellow mechanic friend too.

I did a cardboard test while I wait for the Blackstone to come back. Can anyone chime in and help interpret the test? I’m also having a slight rich trim on one bank at -7% when idling at temp which further leads me to believe of fuel dilution.

 

[dnewton3]

I did a cardboard test while I wait for the Blackstone to come back. Can anyone chime in and help interpret the test?

The "cardboard test" is not a well-defined, quantifiable sequence.
It's akin to any other shade-tree science. Probably the next thing PF will do in a video ...

 

[Urshurak776]

I have seen a few posts in here that say Blackstone's tests for fuel dilution aren't very reliable either...so.....change your oil often.

 

[nicholas]

Hi all,

Did an oil change on an Audi 3.0 Supercharged V6 with 122k miles. The oil was changed after 3000 miles, but about a liter of oil was added half way through the OCI (repaired two oil leaks that one of the repairs involved losing .5 liter)

The oil had a slight fuel smell that was discernible. Admittedly, it was very subtle and not a pungent smell. The smell was confirmed by a fellow mechanic friend too.

I did a cardboard test while I wait for the Blackstone to come back. Can anyone chime in and help interpret the test? I’m also having a slight rich trim on one bank at -7% when idling at temp which further leads me to believe of fuel dilution.

View attachment 209637

View attachment 209638

Is that from 1 drop of oil?

 

[SHOZ]

You should figure out the particle count of the used oil, then add enough soot to virgin oil to match, then do the cardboard test with both.

Then you can judge the ring spacing with new oil.

 

[Treyes1]

Is that from 1 drop of oil?

Yes it is. The image with the light shining upwards such that the cards lines are visible was after 4 hours. The other image where the card is laying flat on the table is the card after like a couple weeks..

 

[camrydriver111]

The best way to validate the test is to mix oil and gasoline in different ratios.

Then perform the test on different ratios of the mixture.

At the same time test your oil sample and compare.

 

[JohnnyJohnson]

Well that certainly beats the taste test!

 

[JohnnyG]

Since gasoline is going to evaporate quickly, the marks on the cardboard mean nothing.
Now, If you were going to get a sample of the fuel oil mixture, weigh it to .0001 gram, heat it to about 100˚F for some arbitrary time, then weigh it again. Using those numbers, calculate a percentage of evaporative loss, then you could compare it to other samples if treated the same way.
Ultimately, it likely won't correlate to increased engine wear, unless it was severe.

 

[Titan]

The actual test is to see how many think the "cardboard test" is useful...reminds me of "anchoring statements" presented in first year psychology classes.