is PLA gasoline, diesel or chemical resistant?
I have used both ABS and PLA for diesel gas caps and oil plugs.  As well have made a gasoline funnel out of both.   Both have done well for me.
I have attach a link to a plastics resistance chart if it is any help.  Unfortunately it does not show testing for ABS for all.  

I prefer the ABS only do to the fact some items I have made sit in the desert sun.  

Plastic resistance chart