all synthetics are not the same. Due to legal allowances, synthetics can be highly refined Group III (dino oil), Group IV (true synthetic PAO), or Group V (esters & other true synthetics) OR a combination thereof. There is little to no regulation of the mixture in the U.S. It used to be (IDK if it still is) that in Europe, an oil could only be Group IV or V if it was marketed as full synthetic.
Depending on the base stock, volatility of "synthetics" could be 11 or could be 6. BIIIG difference (Noack) in how much of the oil gets into the PCV system.