For clarification purposes (synthetic vs dino)...
These excerpts are taken from
https://localtvwtkr.files.wordpress.com/2017/06/aaa-research-report-synthetic-vs-conventional_final.pdf
On March 1, 1999, the National Advertising Division (NAD) ruled on case #3526 involving Castrol
Synthetic Engine Oil. The ruling found that “severe cracking and reforming processes” to hydroisomerize
a mineral base stock is indeed a synthesis and therefore the refined product can be advertised as a
synthetic oil. Because of this ruling, many “synthetic” oils now on the market are composed of highly
processed crude oil..
Groups I-III are derived from petroleum crude oil. Quality conventional engine oils are typically made
from Group II base stocks. They are often manufactured by hydrocracking, a process that saturates the
hydrocarbons within the base stock. Due to the saturation of hydrocarbons comprising the base stock,
Group II oils have good anti-oxidation properties.
Group III base stocks typically undergo a severe hydrocracking process designed to produce a purer base
oil. A significant number of engine oils marketed as “full synthetic” fall into this category.
Group IV base stocks are true “synthetic” base stocks in the technical sense of the word; they are
polyalphaolefins (PAOs) synthesized by oligomerization of α-decene or a mixture of α-olefins containing
between 6-12 carbon atoms. The resulting oligomers are then hydrogenated and distilled to yield the
base stock. Group IV base stocks are lab created, not based upon crude oil.
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Then you have the additives package that is added (detergents, anti wear, anti foaming, anti sludge, etc).
Ideally, those additives should combine with the base stock, but in most cases the additives are mixed
with a crude based carrier and then combined with the base stock.
So even if an oil is a true synthetic based upon group IV base stocks, the carrier used for the additives
package may be crude oil based, so still not 100% synthetic.
So what does all this mean ?
In my opinion, very little when it comes to a snowblower, but good to know anyhow.
In a lab setting, most synthetic (group III or IV based) oils outperformed dino oils in every test, but
in the real world it's probably not so cut and dry.
Out of all the oils marketed/labeled as "full synthetic", there are only a handful that use group IV base stocks (no crude), but they may still use a crude based carrier for the additives package.
Some say there are only 2 true synthetic oils available in the U.S. and others say it's slightly more,
maybe as high as 5 or 6.
For myself, I'll use either Motorcraft 5w30 (since I have a bunch in the garage) or PennGrade 1 (used to be Brad Penn). Both are synthetic blends.