In both the owner's manual, and on some DIY oil change site for maxima's, it says to have the car at operating temp before doing an oil change. I did mine this weekend without, but why does it need to be @ operating temp?

 

warming the oil temp up helps ....the oil thin and drain a little faster..... if the car was cold and had been sitting all the oil was in the pan or the filter.... so other than speed up the drain time... no big diff..... later

 

if you don't warm it up not all of it comes out. so some of your old junk stays in there.