Oil additive f350. 7.3 2001

rbs62 wrote:
What is best oil additive to add to 7.3 with 171000 miles?

NOTHING.

If it is burning/using a little bit of oil, try a "high mileage" type of a name brand oil.

If it is using a LOT of oil, find out why. Additives won't fix that.

P.S. And definitely DO NOT put anything that is a solvent into your oil.....like SeaFoam. It is not really good for any engine and on an old one like that it can turn a minor annoyance into a major failure.