Getting bored and looking for some lively discussion.
I know that some synthetic oil producers have stated that synthetics are more “slippery” or have lower coefficient of friction than petroleum oils. However I would like to disagree with that statement. Based on many fuel economy tests, I know that it is easier to pass the fuel economy testing with low viscosity petroleum oil than a similar low viscosity synthetic. The problem is you cannot pass volatility requirements with those petroleum oils, thus you cannot use to make motor oils.
Think about testing the viscosity of an 8 cSt PAO and an 8 cSt mineral oil. They both flow through the test tube at the same rate, and thus are the same slipperiness. (This only applies to hydrodynamic regime, but the additives are more important than the base oil in other regimes). If you heat both oils to 150 C you will find the petroleum flows much faster, i.e. it is slipperier. At cold temperatures, the PAO is better. So if you want to know which is more slippery, you need to know the viscosity at the operating conditions. It may be either. By the way there are about 2 million different molecules in 8 cSt PAO. And they all look like barbed wire.
I know that some synthetic oil producers have stated that synthetics are more “slippery” or have lower coefficient of friction than petroleum oils. However I would like to disagree with that statement. Based on many fuel economy tests, I know that it is easier to pass the fuel economy testing with low viscosity petroleum oil than a similar low viscosity synthetic. The problem is you cannot pass volatility requirements with those petroleum oils, thus you cannot use to make motor oils.
Think about testing the viscosity of an 8 cSt PAO and an 8 cSt mineral oil. They both flow through the test tube at the same rate, and thus are the same slipperiness. (This only applies to hydrodynamic regime, but the additives are more important than the base oil in other regimes). If you heat both oils to 150 C you will find the petroleum flows much faster, i.e. it is slipperier. At cold temperatures, the PAO is better. So if you want to know which is more slippery, you need to know the viscosity at the operating conditions. It may be either. By the way there are about 2 million different molecules in 8 cSt PAO. And they all look like barbed wire.