Originally Posted by JAG
It being a full synthetic 15W-40 indicates to me that it most likely has thicker base oil mix than the 5W-40 version does, which naturally gives it a higher flashpoint, lower volatility, and less VIIs. Less VIIs will give it more shear stability, assuming they use the same type of VIIs.
I don't buy that explanation. If you look at Delo or Delvac synthetic 15W40, the flash point is no where near 249C. So something other than a thicker base is going on here.
It being a full synthetic 15W-40 indicates to me that it most likely has thicker base oil mix than the 5W-40 version does, which naturally gives it a higher flashpoint, lower volatility, and less VIIs. Less VIIs will give it more shear stability, assuming they use the same type of VIIs.
I don't buy that explanation. If you look at Delo or Delvac synthetic 15W40, the flash point is no where near 249C. So something other than a thicker base is going on here.