Is their an engine oil additive that shows significant results

[hellosailor]

Diesels don't seem to have any special needs regarding oil, seals, or moisture. If anything they used to be less vulnerable to moisture problems, since there was no ignition system. These days if the EFI system is electronics...they're equally vulnerable.

Mercedes took lots of flack in the 80's over their automotive diesels. They often sucked a liter of oil every thousand miles and US customers said that's not acceptable. MB said oh, but this is intentional, and really, it is better. Our engines consume oil because the rings are not as tight, and that allows for much less ring and cylinder wall wear.

Eh, that didn't play out so well in the market. But it does show there is more than one way to design an engine, or excuse the design of an engine.

Sea air may be moist, and it does have higher amounts of abrasive salt (but also nearly zero abrasive silicon dust), but if you run any engine long enough to heat it up, you also cook off any moisture that is in the oil, along with any unburned fuel that has leaked down. This could be as little as 15 minutes but I'd guess it is more like 1/2 hour. So if you start the engine--find a reason to let it run for a while.