408 Break-In Diesel Oil Weight

I ran the Delo 400 in my 340 all summer and it loved it. Using Rotella T-syn 5w-40 now all year round in the two mopars and of course the Cummins. The old school V8s are great with the HDEO oils. I'd stay away from the straight weights in a driver. Not enough pumpability for cold starts. Maybe in a pure race-driven car, but that's about all. Even that is old school. The multi-vis syns are better all around these days.