I always thought there was generally a strong correlation between an engine oil's flash point and the quality of its base stocks, such that an oil with a higher flash point could generally (though not always) be expected to be more resilient at high temps: less shear, fewer deposits, etc. I fully expected there to be exceptions, but I thought that was more-or-less the general trend.
Now I feel like I might have been wrong about that. On the one hand, Castrol Edge Supercar HP -- their Indy Car oil -- has a flash point of 220º C; Mobil 1 FS 0W-40 is at 226º C; and most (all?) of the Pennzoil Ultra line is below 230º C, with some oils only just above 200º C. On the other hand, the dino 5W-20 I'm running now has a flash point of 230º C, and Idemitsu makes an $8/qt 10W-30 with a flash point of 260º C.
Is there no correlation between flash point and base oil quality? Can anything about an engine oil's performance be reasonably inferred from its flash point? If so, what?
Now I feel like I might have been wrong about that. On the one hand, Castrol Edge Supercar HP -- their Indy Car oil -- has a flash point of 220º C; Mobil 1 FS 0W-40 is at 226º C; and most (all?) of the Pennzoil Ultra line is below 230º C, with some oils only just above 200º C. On the other hand, the dino 5W-20 I'm running now has a flash point of 230º C, and Idemitsu makes an $8/qt 10W-30 with a flash point of 260º C.
Is there no correlation between flash point and base oil quality? Can anything about an engine oil's performance be reasonably inferred from its flash point? If so, what?