Thanks for the chance for me to flog this favourite hobby horse of mine Jorge,
In a life that has been blessed with more cars than I deserve I can safely say that I've been through a fair cross section of the oils available out here.... and I've now settled evermore on Castrol's GTX (formerly known as GTX2) mineral oil till death or discontinuation do we part.
Shell's TMO and Helix Ultra, Mobil's 1, Selenia's special Alfa oil (red can), it's generic synthetic (black can), a good few of Agip's oils as well as the best Pennzoil, BP, elf and Petronas could throw at me, and Castrol's own SLX and RS have been in and out of the various engines which have had the misfortune to serve me.
The thing is that once an engine has say 50,000 miles on it the thin synthetic oils begin to find their way around the piston rings and alarming amounts can disappear between oil changes, quite apart from the fact that they don't actually do that great a job of lubricating the engines anyway.
Sure, they don't degrade as quickly as a mineral or a semi synthetic would but at the end of the day I'd rather accept that tradeoff and change the oil every 3000 miles instead of putting up with the coarser engine I get with synthetics to say nothing of peering at the dipstick in apprehension every few days wondering how much expensive synthetic oil I'm going to have to top up this time.
Besides, I'd rather chuck out all the carbon and other deposits that accumulate in the oil every 3000 miles instead of keeping em all sloshing about in my engine for a full 9000.
Dunno what oils you get out your way but that GTX is well worth a try. Worked very very well in all the engines I put it into anyway.