There is nothing wrong with a good semi-synthetic however some of us have practical experience of what is good and bad in an oil, I totally agree with John F ... ignorance is bliss they say ... or in the case of a Subaru turbo engine's it can be self destruction !!

I personally would never use anything else than Motul these days ... in the past I have used alternatives to good effect but ... whenever my car was going to get hard use I ALWAYS changed the oil for a heavier grade fully synthetic.

Remember however that a fully synthetic should only be used in a fully run in engine, untill it reaches that state I would strongly recommend restraint and "conservative" (ie no track days) use.
cheers

 

another spanner being thrown!

Viscosity of oils isn't only important for temperature.....

It also vitally important for maintaining good oil pressure and cushioning mechanical shock.

I seem to find that the thinner the oil the tappier the engine.

Plums.

Running with Motul 15W-50!

 

Bob, what's your opinion on Castrol RS 10W60 ? Is Motul a better choice still, and if so, why ?

 

My dealer used semi synthetic Shell Helix oil, they will not use anything else. My MY01 has done 20,000 mls on this stuff without any problems. I would say however i do a 5000mls oil and filter change myself between each 10,000 mile service using the same Shell Helix oil.

Cheers

Les