Yes, I have looked up dozens of the SeaFoam vids after stumbling on the first one a couple of months ago, to be honest I tend not to ask about additives here as you can get a right old roasting from the "Snake Oil" brigade who still think electronic ignition in distributors to get rid of points to be sacriligeous and a perversion of nature
There is an American product from Lucas
Lucas oil Heavy Duty oil stabilizer Does it really work? Friction test that I want to try on the old 200Tdi, I've used molyslip in the past with good results in quieting the valve train and also using Wynns "Super Charge" for oil, I used that on the little Peugeot 206 a few months ago after the second oil change and it really helped to reduce some of the rough noises that came out of the engine, smoother and much more refined after that, just the SeaFoam treatment now to try and loosen up and dispose of some of the built up carbons in the rings and combustion chambers and I think it will be back up to a reasonable standard of health.
Obviously I would rather strip it and rebuild it but I also have to factor in the life span of the vehicle, 19yrs old, very basic 1.6 petrol car, doubt it will see another 5yrs under my ownership as I hope to move her over to an all electric car within 2yrs but it is her learners car, my 200Tdi Discovery is being built to take us through the other side of the zombie apocalypse and nothing will stop me from rebuilding the old lump if ever it needs done.
The obvious thing on older trucks is to up the maintenance levels and change oils more frequently than the manual states and especially if they get worked hard in harsh terrains, nothing will last forever when test to it's limits regular