So good points frank. What rpm is your engine pulling on long haul towing? Over 4K? The big concern I have is the results of pulling 3-5k rpm for extended time.
I did put in a good after market pump (not a high volume to avoid draining the pan). Also a major problem from mid 2000’s on is that DOD garbage. Under the valley plate is a series of sensors and stuff that shuts off the lifters at certain rpm. A major issue are those lifters collapsing.
Vs the ls7 lifters here
This is why DOD deletes (LOMA, AFM- all same thing) are so popular. In addition, vvt and a cam phaser can be part of this but my gen 4 didn’t have vvt.
So what they told you makes sense for a stock engine (with DOD and VVT) running in cold weather. As 5w and 0w are the measurements for how it will flow at colder temps. Here in Hawaii as in FL it’s pretty warm all the time.
What’s got me scratching my head, there doesn’t seem to be a standard-Crusader has one and VP has one -they are both using LS now are calling for much thicker oils over GM’s factory specs. I actually called Royal Purple to discuss this but couldn’t reach anybody. There are even some guys running VR-1 a race oil at 20w-50 in boats and race cars with great results. However I’m not sure a standard volume pump can handle that. I’ll do some more research on that.