That's the problem with the 5w30's, they run great you think it's fine but if you do a UOA you'll often find you could've done much better.
A 4.0 will usually shear a typical 5w30 with a [email protected]
of 10.5 down to about 9 in only 3,000 miles. At that point it's too thin for optimum protection, the 4.0 needs thicker lube than that.
It will also do the same thing to lesser 10w30's, so if running a standard thickness 10w30 a top quality name brand needs to be the choice. Valvoline has been the stand out in this bracket Maxlife or White bottle no matter. Better yet though is a quality 10w30 on the thick side, like Rotella or Defy.
Ironically I can count the "good" UOA's I've seen for the 4.0 using top tier synthetics on the fingers of one hand with some left over. The 4.0 thrives on a good dino or at most a syn blend like Maxlife or T5.