Alright so this is my question. I now have to change my own oil due to the fact that I have moved across the country away from the dealership that was giving me lifetime oil changes. No problem with changing my own oil. What I am wondering is the Hemi truck is supposed to have 5W-20 in it. I am going to use mobil 1 but I wanted to purchase my oil at Costco to save some $$$. All they have is 5W-30. Any other time I would add this without worrying. However this is Chrysler. Will this oil be affect my engine performance in any way (MDS?), will it void my warranty at all?