How sensitive are the 3.9 engines to oil viscosity? I've read that you absolutely have to use 5-30 in my 08 impala but I have 10 jugs of PP 10-30 that I wanna use up, probably next summer and fall. I have disabled the active fuel management if that matters, but believe it or not, this is my first Chevy @46 yrs old. Anyone have some testimony here?