Here are my 2 cents:
1. Delo 400 is primarily a diesel engine oil for commercial fleets. It is formulated to also meet most gasoline engine specs so that it can be used in mixed fleets.
2. Delo 400 does not come as a 10W-40; it comes as 10W-30, 15W-40, and 10W, 20, 30, 40, and 50 single...