If you can find a lab that directly measures VI, test your own sample, and I'll pay your donation...how's that ?
If you can only find one that measures KV40 and KV100, and calculates the VI, then you are on your own.
The 236 IS the viscosity index that arises from the KV40 and KV100 that the lab that Gokhan used measured.
The viscosity index for the MSDS, which is hardly a product data sheet IS 225.
Both are a dimensionless number, calculated from two measured numbers.
If anything is in error, then you are arguing with the the KV40 and KV100 results, and the difference between the tests posted in this thread, versus the MSDS.
Given that ideally, the sample and equipment need to be within +/- 0.02C, and testing should ideally take minutes of flow, it's unlikely that viscosity can be measured in a quick lab, even calibrated properly to within a percent up or down. And that percent is probably of full scale, not the measured value...
not sure on how long the machine takes to get up and down to temp, so it's unlikely (IMO) that KV40 and KV100 are measured on the same machine even.
Take the Mobil MSDS figures, and say they are on the same machine for argument's sake, to rule out a variable.
Say that the machine has a full scale of 50, as if it can measure way more than the viscosities in question, it's accuracy at KV100 will be worse...each measurement is therefore +/- 0.5cst.
KV40 of 36.1 can be 35.6, or 36.6...will be somewhere in between,
KV100 of 8.5 can be 8, or 9. Similarly, it will be somewhere in between.
VI can therefore be anywhere from 200-249, and still be correct.