Originally Posted By: chevrofreak
Paraffin is a very misused term.
Agreed. In Chemistry, paraffinic = alkane... that is, a linear or branched (but not cyclic) hydrocarbon in which all the carbon molecules are completely 'saturated' with hydrogen atoms (no double or triple carbon-carbon bonds). Group III / III+ oils are highly paraffinic, meaning they contain very few unsaturations.
Group IV oils, conversely, are typically based upon n-alkenes, meaning they are linear hydrocarbons in which the first carbon atom and the second carbon atom in the chain contain a double bond (unsaturation), and the rest of the carbon atoms in the chain are 'saturated'.
Group III/III+ and Group IV oils each have their benefits as a base oil for lubrication, but both are vastly superior then the Grp. I and II oils of the past, which contained larger amounts of naphthenic and aromatic compounds.
Hint: don't confuse 'paraffinic' with 'paraffin wax'. paraffin wax is a type of paraffinic compound, but not all paraffinic compounds are waxy solids.
In the 'old days', Pennzoil got a bad rap because apparently pennsylvania crude had a higher content of paraffin wax than is desirable in a motor oil. This apparently caused sludge. Pennzoil is no longer made from pennsylvania crude - and even if it was, the refining process is so much better these days that it would eliminate all the wax from the base oil anyway.