Originally Posted by jonklein611
Because most 5w-30's are what Uncle Scotty calls "girly man" oils. AKA they suck.
Very very few 5w-30s are inexpensive and protect as well as Rotella.
OT/Slight thread hijack.
I'm actually being bold right now and trying a Motul oil with girly man levels of ZDDP. X-clean C3 5W-30. It's SM rated, but it doesn't get the official girly man Energy/Resource Conserving seal because it meets Euro ACEA A3 specs with a higher High Temp High Shear and it's also thick at 100C like GC (which gives me some comfort). Low TBN though so I won't be pushing it too far. Although someone here did a 7,500 mile run in an STI (and without a TBN reading).