Actually, it is the other way around. The easier a liquid flows the less viscous it is.
I guess it has to do how easily the molecules in the fluid can move around each other. Liquid N2 (small, non-polar molecules) has very low viscosity, and liquid helium-4 at temperatures near absolute zero has NO viscosity(!), which makes it possible for it to flow out of a non-tilted beaker.
The longer a molecule is, the harder it is for them to move around each other, that's why butane (C4H10) is less viscous than gasoline (about C6-C8), which in turn is less viscous than kerosene (even longer carbon chains). If polar groups are attached to the molecule, that makes them stick together, that is why butanol C4H9OH is more viscous than butane, and butanediol HO-C4CH8-OH is even more viscous.
http://rhodium.lycaeum.org