Oil Analysis proves that any of the group products will meet or exceed your mileage
expectations because they all strive to deliver pure uniform molecules...
Refining means removing less desirable elements from petroleum until
what’s left is mostly higher-performing molecular structures. Waxy
stuff had to go because it made oil congeal at winter temperatures.
Aromatics had to go because they lost viscosity too rapidly when hot.
Unsaturates had to go because they were vulnerable to heat-driven
gumming and sludging. And so on.
Group I: Petroleum oil containing 10–30 percent aromatics.
Group II: Hydrotreated mineral oils. Hydrotreating removes compounds
of oxygen, nitrogen, sulfur, chlorine, and metals.
Group III: Severely hydrocracked oils, the extensively reformed
"synthesized hydrocarbon oils" of today. Hydrocracking converts heavy
oils into lighter fractions by saturation, breaking large molecules
into smaller ones and creating from the fragments desired isomers.
Single-pass isomerization can boost the Viscosity Index (VI) of a
Group III base stock by 30 percent. VI indicates the rate at which an
oil's viscosity decreases as temperature increases in roughly the
range between cold and hot engine temperatures. The higher the number,
the better the oil covers the range of temperatures.
Group IV: The dominant automotive synthetic today is PAO
(Polyalphaolefin) + AN (Alkylated Naphthalene) + diesters, as found in
synthetic engine oils like Mobil 1. PAO delivers exceptional VI and
low pour point, while its tendency to shrink seals are corrected by
added AN and diesters. The PAO itself is synthesized by polymerizing
simple gas molecules derived from natural gas, and then connecting
these short hydrocarbon chains to form comb like structures.
Group V: Esters, polyglycols, silicones, neopentyl polyol esters, and
others, which are synthetic or chemically engineered oils not falling
into previous groups. Many are familiar to bike racers of the 1970s
through 1990s because they have been the basis of two-stroke racing
oils. Some of these oils can have higher VI, oxidation resistance, and
resistance to thermal breakdown than do PAO-based synthetics. R&D
never ceases in the chemical industry.