If your in an oil cooled turbo car, then 0-30 and 0-40 protect the turbos on start up by helping oil flow through the lines quickly. If the srt6 has an oil cooled super charger and lines bringing oil in, it would be smart to use the 0-40 from mobile 1,0-40 castrol(new), or LUCAS makes a decent 0-30 &0-40. 5-40 from mobile1, Amsoil, castrol, penzoil, royal purple, Lucas, seem ideal for the N/A motor( just pick the brand you like best). If there are no oil lines cooling the blower, 5-40 should be fine.