they are both petroleum based, its just that one is conventional and the other is made in labs.

mobil 1 I believe is a group III. it's a synthetic but not a TRUE synthetic

it sounds like he means regular old 98 cent cheapo oil. I have no idea how or why synthetic would be BAD for cams. I could see the break in period taking longer, but again I really dont see how it could be bad

mobil 1 is synthetic blend not full so were does that stand in? more on the base side?

Y'all are close, but not quite right...

To put it simplistically, conventional oil is refined from crude oil that's pumped right out of the ground. In the bottles that you buy, it's about 80% petroleum product and 20% additives (which may be either synthetic or naturally-occuring additives, actually). Things like viscosity index improvers, anti-scuff agents, friction-reducing materials, and detergents. But in the end it's mostly just oil that's basically refined from what's pumped out of the ground. This is most of what you find on the shelves.

On the other end of the spectrum are the Group IV type oils. These are truly, full-synthetic oils, produced in a plant rather than pumped out of the ground and refined, with PAO and ester bases. Desirable characteristics in engine oil can be engineered into these oils by altering the chemical makeup. The additives are similar, though obviously different in specifics because of the difference in where synthetic oils already start out. These are some brands of Group IV oil: Amsoil, Red Line, Motul, Royal Purple, Elf, Eneos, and only one type of Castrol Syntec, the 0W-30 "made in Germany" European formula.

Now, a little while back Mobil discovered that what Castrol was advertising and labeling as "synthetic" was in fact not truly synthetic, but instead a highly-enhanced, pumped-out-of-the-ground type base. The API decided not to make a true definition for "synthetic" oils, and Mobil sued Castrol...basically, the court ruled that Castrol's oil was engineered enough from the base that it could be called "synthetic." As a result, Mobil 1 "synthetic" soon changed in formula from a true Group IV synthetic, to a lesser Group III oil. Group III oils start with the same exact stuff as regular conventional oil...it's pumped out of the ground and refined into a product. But it then undergoes processes called hydrocracking and isodewaxing which wind up mimicking some of the properties of Group IV synthetic oils. These "fake synthetics" make up the majority of mass-marketed synthetic oils today. Castrol Syntec (except the one type mentioned before), most Mobil 1, Pennzoil Platinum, Valvoline, and plenty others are all just Group III oils, petroleum-based but highly, extensively refined...and of course, with an addtive package to complement it.

Synthetic blend oil is a joke, by the way. If you ever pay extra for anything labeled "synthetic blend," please kill yourself. Basically you're buying 100% petroleum based oil, but a certain part of it (never 50%, of course....usually no more than 20%) is a Group III, highly-refined petroleum based. So if you buy 5 quarts of synthetic blend oil, best case scenario you now have four quarts of regular old conventional, and one quart of Group III "fake synthetic."

Now you know

So what would be the best "fully synthetic" motor oil to buy? I was under the impression that it was Mobil 1