TomicaGTR,
It depend on your engine modifications.
For stock condition you may use the:-
1. MOTUL Semi Synthetic Turbolight 10W-40 or (Smooth minimal Tapped sound)
2. MOTUL Fully Synthetic 8100X-Cess 5W-40 or (very light but produce Tapped sound)
3. MOTUL 300V Fully Synthetic Chrono 10W-40 (higher budget)
But, if any modification been done means more HP will be generate along with others.
1. MOTUL Semi Synthetic 6100 Synergie 15W-50 or (little bit heavy feeling on my engine but smooth).
2. MOTUL 300V Fully Synthetic Competition 15W-50 (higher budget)
4G63T, normally will generate Tapped Sound (but have to make sure due to what reason).
when use thinner oil (depends on your engine condition).
I've been used and tried the above mention.
And satisfied on it...
For time being I run my 4G63T using Semi Synthetic Turbolight 10W-40.
All running smooth in town + long distance.
If for "test" the ride i will swap to Chrono or Competition depend on event.
Above all you also need good oil filter. Recommend the K&N oil Filter.