White powder baked on exhaust tips

[sneaky7980]

I just noticed after a 11 hr roadtrip, no rain, that the exhaust tips on my 99 T/A have white stuff on them. It seems to "baked" on right at the tip of the openings. I also had my low oil light come on this morning and sure enough it was 2 quarts low. I've owned the car for a few months and it has always had a little rough idle but runs fine. Should i be worried?

Extra info;
Car is completely stock
Synthetic oil
Use premium unleaded
44k miles
BTW i was givin her hell on the trip

[sneaky7980]

any thoughts?