i went to summit racing for redline oil and they only had 2 quarts of 5-30 so i picked up 2 jugs of mobil 1 5-30 extended to use in my 2 twin turbo stealths. although this is basically a winter storage oil should i get some zddp additive. i see summit racing has a couple of different brands of this. i cannot find any info on zddp in mobil 1 5-30 extended oil. the jugs states meets slm,n and bc 4 and 5 so what do you folks think about the mobil1 5-30 extended oil??? thanks