It's widespread knowledge that paper or cardboard contaminated with oil can cause problems in the recycling process, and an often stated rule is that contaminated material should not be recycled.
However, it would make sense that low levels of contamination are ok.
Are there any widely accepted tolerance levels for contamination by oil, or does it differ depending on the recycler (or worse, do they not even define it)? What are the acceptable levels, if there are any?
If information is available on acceptable levels of contamination with other substances, that would also be of interest.
Somewhat related questions: