Originally Posted By: Ben99GT
Originally Posted By: beast3300
At work we use 5w20 plain Jane Valvoline in everything that calls for 5w20. None of the commercial vehicles that get the #$%% beat out of them come in knocking etc. They are tough and designed for 5w20. I wouldn't change a thing, your in good shape with the MC 5w20 blend.
We'll never know without an oil temperature reading, but I'd be willing to bet oil temps can creep pretty high with a load that massive. Better to err on the side of caution when going that far outside of the OEM's parameters.
I really don't feel like dredging up Scott Whitehead's (Ford systems engineer for the 2005 4.6 3V and 2003 4.6 4V) comments again, but I will. Let's just say the man behind the 4.6 3V and 4.6 4V, who has torn down dozens of these engines during durability testing, isn't the biggest fan of 5W-20s in severe service.
No argument from me (not a Ford fan). However, I have seen many commercial vehicles 3 qts low on a 8k mile OCI with over 200k. Just food for thought.