Oil Question

[veebee]

i'm sure this has been asked about 5000000000000 times, but a quick search didn't yield any helpful results

my pal who installed my sr (s13 blacktop with s15 t28 if that makes any difference)used castrol 10w-30 oil. i thought turbocharged engines needed synthetic? he said it doesn't really matter, but he does change it more frequently (about every 2k miles).

does it matter if i use full synthetic or not?