Every engine oil manufacturer will have a specification sheet on the website. If that sheet doesn't tell you the flash point, the Material Safety Data Sheet will, and they are required by law to offer that document to you.
From Mobil 1's website:
Mobil 1 10W-30
Flash Point, ºC, ASTM D 92 =224 [degrees C; = 435.2F]
Mobil 1 EP 10W-30
Flash Point, ºC, ASTM D 92 =230 [degrees C; = 446F]