Synthetic has changed in recent years. A little history first....
In the days non synthetic oils were group 1 and group 2 base stocks. These are crude oils and polyphenins. Synthetic was as it was stated group 4 and group 5 base stocks which are PAO and POA esters (man made extreme quality esters which mimic esters once used from whale fat).
Then came the big Mobil 1 vs Castrol lawsuit. Mobil 1 contended that Castrol was using false advertising. Castrol had changed there formulation on there Full Synthetic oil. It NO longer was made from group 4 synthetic base stocks but was indeed made from group 3 base stock which is a conventional crude base stock, then severely hydro cracked and refined. group 3 is much higher quality than group 2 oils. Well it made it all the way to the supreme court were they ruled that oils made with group 3 base stocks are indeed synthetic because of the extreme amount of refinement, it isn't anything naturally occurring anymore. So Castrol was allowed to continue marketing the oil as fully synthetic. After this lawsuit a precedence was set for the definition of synthetic oil, one by one manufacturers started reformulating their synthetic motor oils from group 4's to group 3's , since group 3 is much cheaper to use.
This brings us to today most so called synthetics are just dino oil (conventional). Dont get me wrong the group 3 is far superior to group 2 it has much better flow characteristics in the cold and better resistance to heat. But you still are only using a conventional crude oil that is ultra refined.
Here is a list of the only Oils that are true full synthetic (groups 4 or 5).
Mobil 1, Amsoil, Royal purple, Redline, some Schaffers, some Motul, Valvoline synpower is a blend of goup 3 and 4, Castrol makes (1) full synthetic it is 0w-30 only and has to say made in Germany on the bottle otherwise it is group 3,the bargain oil out there is Valvoline maxlife synthetic blend which is group 4 and a group 2 blend it performs really well at a reasonable price.

ok Now YOU know the difference time to decide,
group 4 and 5 do outperform the others, but by how much ??? Oil has come an incredibly long way. No longer do we utilize crappy group 1 basestocks (at least not much). Now most convevtional oils in fact are group 2 group 3 mixes to meet ever tightening lubricant requirements and tests. The pseudo full synthetics which are group 3 and really good oils, one of the best is Pennzoil Platinum actually probably the best group 3 oil on the market.
My advice is to decide will you extend oil change intervals out 6-10,000 miles to make true use of the true full synthetic, do you subject your vehicle to severe conditions do you start your vehicle in subzero temperatures if so then synthetic may be your thing...........come on over to bob is the oil guy forum and learn much much more about oil........
Source(s):
http://www.bobistheoilguy.com/forums/ubb…