Halderman: The following is from one of my textbooks that explain the various groups of oils and “synthetic” oil can be from group III, IV, or V. I use Mobil 1 which is mostly group IV with a little group V to swell the seals. I hope this answers your question.
“Group I. Mineral, non-synthetic base oil with few if any additives; suitable for light lubricating needs and rust protection, not for use in an engine.
Group II. Mineral oil with quality additive packages; includes most conventional engine oils.
Group III. Hydrogenated (hydroisomerized) synthetic compounds commonly referred to as hydrowaxes or hydrocracked oil; the lowest-costing synthetic engine oil; includes Castrol Syntec.
Group IV. Synthetic oils made from mineral oil and monomolecular oil called polyalpholefin (POA); includes Mobil 1.
Group V. Non-mineral sources such as alcohol from corn called diesters or polyolesters; includes Red Line synthetic oil.
Groups III, IV, and V are considered to be synthetic because the molecular structure of the finished product does not occur naturally, but is man-made through chemical processes. All synthetic engine oils perform better than group II (mineral) oils.
Pros of synthetics
The major advantage of using synthetic engine oil is its ability to remain fluid at very low temperatures.
This characteristic of synthetic oil makes it popular in colder climates where cold-engine cranking is important.
Cons of synthetics
The major disadvantage is cost. The cost of synthetic engine oils can be four to five times the cost of petroleum-based engine oils.
Synthetic blends
A synthetic blend indicates that some synthetic oil is mixed with petroleum base engine oil; however, the percentage of synthetic used in the blend is unknown.”
James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your questions to Halderman via e-mail at jim@jameshalderman.com or follow him on Twitter @jameshalderman, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
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