How this flash point is achieved?

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I was browsing around and curiosity took me to this Shell HX3 20W50.


I found the flash point of 256 degree celsius to be very interesting. From a VI of 126, I can safely bet it is a group 1/2 blend. I haven't seen a lot of synthetic oils with this high flash point. Is Shell telling the truth?
I don't see any OEM specifications on this oil. But the question still remains, how a group 1/2 blend can achieve this?
 
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ASTM D92 is open cup testing, make sure you're comparing against the same ASTM test. It's been a while since I've done flash point testing so I can't remember which one is higher or lower.

Are you concerned your oil is going to ignite in the presence of a flame?
 
ASTM D92 is open cup testing, make sure you're comparing against the same ASTM test. It's been a while since I've done flash point testing so I can't remember which one is higher or lower.

Are you concerned your oil is going to ignite in the presence of a flame?
Not concerned at all. I don't even fill 20W50 in any of my engines.
I'm just curious how this oil has a relatively high flash point among its class. I guess you gave me an answer. Thanks.
 
Not concerned at all. I don't even fill 20W50 in any of my engines.
I'm just curious how this oil has a relatively high flash point among its class. I guess you gave me an answer. Thanks.
No I didn’t really. I don’t know what test is used for the ones you were comparing against and I don’t know which test is higher or lower. I’m just saying to make sure you’re comparing apples against apples. That value you’re referencing may very well be a typographical error.
 
I doubt Shell would lie in their data sheets, i've used HX3 20W-50, it's a very old school oil and almost certainly all Group 1 and with a thick base oil, generally the thicker the base oil, the lower the Noack and higher the flash point.
 
Like FCD said, an oil formulated on thick base stock such as a 20W-x, should have a lower vapour pressure and a higher flash point. While an oil formulated on thinner base stock such as a 5W-
-x should have the opposite (higher VP and lower FP).
 
ASTM D92 is open cup testing, make sure you're comparing against the same ASTM test. It's been a while since I've done flash point testing so I can't remember which one is higher or lower.

Are you concerned your oil is going to ignite in the presence of a flame?
Quoting myself from the past:
Regarding flashpoint:

There are two different methods used:
ASTM D92 - Open Cup
ASTM D93 - Closed Cup

Closed Cup produces lower numbers because vapours can't escape.

Mobil is all over the map, as they use both methods, seemingly at random, and you'll consistently see the D93 results are significantly lower than the D92 ones.
 
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