Oil blotter test

[harthamm]

I have seen the oil blotter test mentioned a few times. I have tried it on business cards and coffee filter paper - Interesting.
Is this actually a useful test or am I just as well served with tarot cards and tea leaves?

 

[harthamm]

I forgot to add I do this on warmed oil. Is this correct?

 

[Highroller]

It's a good test and easy to do method.

 

[Highroller]

I usually warm the engine before testing it.