Honda recommends 10W-30 or 5W-40 in the S2000.
I contacted Mobil support and they recommended their 0W-40 and OK'd Delvac 1 5W-40 after I asked specifically about that product.
I currently have M1 0W-40 in the car, it is much easier to find, but I am concerned about the shear stability w/ the spread. I do 3K oil & filter changes and occasionally track the car at driver's schools.
From reading the UOA and VOA forums, the main difference between the 2 oils is that M1 has some molybdenum and D1 has no moly but much more phosphorus.
As Honda is recommending what is typically a fleet/diesel weight oil and doesn't specify ILSAC GF3, I do not see catalyst poisoning as an issue.
Is the moly more beneficial then increased phos? Is the opposite true? Is there any downside to the D1 in this application?
Thanks and regards, W&w