Suigi S6000 is 10w40.
Gulf 1 is 10w60.
10w60 is great.... for tired engines with poor tolerances and/or serious blowby problems. Not something you would want to put in a RB which has 7.5w30 specified by factory (10w40 taking into fact our warmer climate).
The 60 rating is nice and thick for track duty, though if the engine isn't built for it (ie. no sump mods or extensions, head restrictorss), the thickness of the oil will have trouble draining back to the sump and the engine will end up with oil starvation.