Hot Idle oil pressure is 20-22 psi. 1750 rpm is 45-47. Delvac ESP 5w40 is a little lower. Max is in the 70s but I believe the oil pressure starts to open at that pressure so you won’t see anything higher.What does the oils pressure look like on 10-40? I have seen high 70s during warm up on 5-40.
No $h!t Sherlock Holmes. All CJ-4 and CK-4 oils have an ash value of 1.0%. They are modern HD oils designed for extended drain intervals and be compatible with DPF, DOC and SCR systems.Worth noting, the Mobil 1 Delvac ESP 5W-40 oil has a sulphated ash content of 1%. The Mobil 1 ESP 0W-40 oil (Dexos 2 approved) has a sulphated ash content of 0.8%, which is 20% less.
It seems like running the lower ash content, plus knowing you are staying with the GM recommendation for Dexos 2 means the Mobil 1 ESP 0W-40 might be a better choice for the LWN. Even if you feel strongly that you want a full synthetic 40 weight oil, there is a Dexos 2 approved option.
The Dexos 2 0w40, like all 0w40s are very light. They are only marginal low density 40w oils and the Mobil version has essentially the same HTHS as the 5w30. A HD 10w30 will still have a higher HTHS and provide a thicker oil film than the 0w40 mentioned above.