Something I've been thinking about lately. When I bought my truck last year, the PO didn't do really any maintenance at all. He had it about 9 years (friend of a relative, good chap but not a car guy).
So I put in new oil and a filter. I strongly suspect he did not have the oil changed for at least 3 years, more than likely it was older than that. Long story short the oil was blacker than hell and I'm pretty sure the oil filter was in bypass mode.
Anyway I've put a few thousand km on it now with fresh oil & filter but I'm still thinking maybe I should put an additive in the oil to help clean things up.
I'm seeing some posts on Marvel Mystery Oil (MMO). If I was to add say a half quart now and change the oil again in a month does that sound like a good plan? I think the oil is in pretty good shape but I can just imagine there is crud in the engine.
Also, is it safe to run the truck daily (and during winter) with 5 quarts regular oil plus 1 quart MMO? I have the oil already to do another oil change, just thinking about my options.
Background, I recently swapped gauge clusters so I actually know what's going on with my oil pressure now. At startup and for the first few blocks the oil pressure is pegged high, but after that it is totally normal (I compared the specs to what the owners manual says).