This may be a topic that has been beaten to death before, but I'm new to the 6.7 world (had a 5.9 years ago). The manual says 5W40 synthetic for under 0 deg F and 15W40 otherwise. I'm in Colorado, so it does get that cold a few times a year, and I don't have a place to plug the block heater in at work. I did quite a bit of internet searching before this with mixed results. However, most results were from when people's trucks were brand new. Mine has 100k miles on it. I know that's not a lot for a diesel, but I'm wondering if anyone has had any oil pressure issues with 5W40 during the summer with higher mileage engines. I'd probably go for Rotella 5W40 T6 Synthetic because that's what my Liberty CRD runs as well. I just want to make sure I'm not going to have summer issues.