Buy your 5 quarts of 5/30 so you have you receipt for warranty then sub a quart or so with Pennzoil 5/40 or 0/40 it may help to keep it in the 30 weight range between your intervals and boost the HT/HS viscosity a bit. Most resource conserving 30 weight oils in "that" motor are going to end up as a 20 weight rather quickly.
But if a dealer decides to have the oil analyzed (probably unlikely) they'll know an xW40 was used if the viscosity does not come back as a 20 grade.
Lol...Yeah your probably correct on that.
Well if you did add a quart or so of a 40wt as long as it ended up as a 30 weight, if there was ever an issue, they would have a pretty tough time with that argument. If you have been there and done that it wouldn't be a fun experience regardless of the oil used. It would be painful either way to deal with.