Its about volume.
  Spontaneous combustion in a fairly dry rag is pretty dim.
If you go crazy and soppy soak a bedsheet (big rag) with gushing amounts 
of oil?
Then leave it wadded up on the edge of the porch?

My good friend of almost 50 years just lost his home and barn/shop.

do not screw around
Personally I do not use a rag at all.
A few drops applied with my bare hands saves on oil and danger both.
yours Scott

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*******************************
    Scott Grandstaff
    Box 409 Happy Camp, Ca  96039
    scottg@s...
    http://www.snowcrest.net/kitty/sgrandstaff/
    http://www.snowcrest.net/kitty/hpages/index.html