Not trying to steal the microphone from EB, but I have lots of experience with SYN lubes.....Overall, they are better.

The thing to remember with SYN oils is they are designed/formulated/constructed to do what fossil based oil is "adapted" to do....And that SYN oils do it better and longer.

Lubricating oil has a big job. It has to prevent metal-to-metal contact between parts that are subjected to violent forces and also carry heat away from those parts. And while it's doing all this, it can't suffer or breakdown under those conditions. SYN oils are better at this than fossil oils.

Proper lubrication is achieved by not just the selection of oils used, but also by design of the components you need to lubricate.....cranks/rods with larger bearing surfaces offer a larger area for oils to work, but they also must be clearanced properly to allow sufficient oil flow......flow carries fresh oil thru the bearing and removes heat.

Race engine builders learned long ago to open up bearing clearances to allow more flow. They also learned to increase journal diameters and campher/polish surfaces....Increased clearances allow more flow, canphered/pollished surfaces offer less restriction to flow.....larger bearing surfaces spread the force out reducing the chance that forces will overcome oil film strength......But in order to support larger bearings and bigger clearances, then you had to pump more oil-flow more oil.....

That's when they developed High Volume oil pumps.

That said, then installing a High Volume pump on a stock clearanced engine only caused higher oil pressure, not better lubrication....And the possibility of flow induced bearing errosion became a worry.

Pressure urges flow, and flow insures fresh oil to carry away heat, but flow only happens if clearances allow it, right?

So that said, then you can follow that proper lubrication is a balance of many things....It depends not just on pressure, but also flow. It needs to be balanced and controlled so that all bearings get enuff oil to not just keep a film, but to also not overheat....Syn oils do all this better than any fossil oils can ever hope to....But the engine builder has to help by designing the engine to allow sufficient oil flow at every place in the oil path.

The lube engine designer is restricted in his efforts by several brick walls....First is the temp extreems the engine will face in normal use-from Alaska to Vegas. Then there is actual engine design....the path the oil must take from the sump all the way thru the engine and back to the sump. He has to calculate the requirements of each friction surface and work with other designers in a balancing act....Most engines send oil first to the crank and rod bearings, then port that same oil to the cam and finally the heads and rockers.....as that oil flows along that path it picks up heat and gets beat pretty hard....by the time it reaches the cam/lifters, it has already done a hard job and it is there where it experiences the final torture.

On many engines, the cam/lifters/followers attempt metal-to-metal contact like no other place in the engine....add to that the tremdous heat produced by the head from the passage of cumbustion gasses thru the ports and the fact that this oil is farthest from the pump and at it's least level of pressure/flow, then you can understand that this is where most oils lose the battle and break down....SYN oils resist that breakdown best in this area....this is where they shine.....This is where they win over fossil oils.