Well after 10 000 km it is fair to say my engine is well broken in (piston rings seated etc..) so I finally made the switch to 100% synthetic oil. I decided to use :
MOTUL 300V Competition 4T 15W50 Ester-based, 100% synthetic.
Winner of the most famous endurance events: Bol d’Or, 24 hours of Le Mans, 8 hours of Suzuka, Daytona 200 Miles.
STANDARD : API SG, CCMC G-4, JASO T 904 Friction.
RACING (high performance engines and intensive riding) The 300V range is specifically designed to withstand both the severe conditions inherent in racing and the demands of a rider pushing his machine to its limits. This range of lubricants is perfectly suited to competition conditions from road-racing to endurance, motocross to six-days enduro.
Because they are ester-based and enhanced with highly efficient and specialized anti-friction additives, the 100% synthetic 300 V lubricants need no or little viscosity improver additives. An exceptional resistance to shearing from one oil change to the next is therefore maintained.
The main performance figures common to the whole range are:
A drastic reduction of friction within the engine, that results in better performance and reliability, a lower noise level and less wear on moving parts.
Reduced engine running temperature.
Exceptional coking resistance (i.e. carbon build-up) at high temperatures.
Low volatility (i.e. very little high temperature evaporation).
These characteristics make 300 V Racing 15W50 and Sport 10W40 (the viscosity depends on the hydraulic pushrods) the lubricants that are recommended and used by leading racing teams. They ensure engine reliability and increased mileage.
PRACTICAL ADVICE
Consult the manufacturers’ recommendations and adapt them depending on the vehicle’s use.
My decision is made based on the overwhelmingly convincing truth that:
1.) engine start is drastically reduced
2.) life of the engine is increased due to 15 to 20% less friction (only makes sense)
To me that easily justifies the 100% price increase of regular engine oilExtended Service Life - Synthetic Oil uses only the best additives available, to provide extended drain intervals in gas vehicles, 25 - 35,000 miles or 1 year. In diesel engines 2x manufacturers recommendations.
I will still change the oil every 5000 km...the idea is to flush out contaminants not save a few bucks 
start-up protection - Sixty percent of all engine wear occurs at startup. Synthetic Oil's use high polarity base stocks and special anti-wear agents that form a thin film that clings to engine parts, preventing metal to metal contact.
Thermal/Oxidative Stability- keeps your engine clean, reducing costly maintenance repairs, adds life to your engine.
Superior Friction Reduction - less stress on your engine providing superior gas mileage increase and additional horsepower. Reduced friction makes engine bearings rotate easier. This saves energy and conserves fuel. Synthetic Oil will save you enough per year in fuel savings to pay for all your vehicles lubrication needs.
Low Volatility - allows best air flow which provides less oil evaporation, providing best fuel economy and engine wear protection.
Broad Temperature Range - provides protection in hot or cold extremes, adding longer engine life. Friction generates heat and since Synthetic Oil reduce friction, less heat is generated. Synthetic Oil also carry heat away from the engine more efficiently than conventional oils to further enhance the cooling process.
Extremely High TBN - increases oil life by reducing engine corrosion, which adds longevity to your engine and reduces maintenance costs.
