Is it safe to purge a 300SDL?!?!?!
 

Is it safe to purge a OM603?? It says "No additives" at the fuel area but i am not inducing diesel purge into the fuel tank...getting a little confused here....

Yes. It is safe. The "No Additives" was made in reference to that old infernal trap oxidizer football canister thingamajigger which could cause internal damage to the turbocharger and potentially engine. This apparatus should now be absent from your car. Now that (I'm assuming) you have the Ox-Cat in place, you shouldn't have to worry about plugging up the "trap".

An '86 300SDL (federal) will say "DIESEL", and that's all.

Yeah, you're safe...

yes

I think DP is a waste and won't use it anymore.

If your injectors are iffy remove them for testing.

I doubt you will hurt anything, worse case you knock some crap lose and clog a nozzle, but I doubt it will do anything either.

My car has the "no additives" label in front of the filler, but it didn't come with a cat.

DP helped me out with some mild nailing a year ago, so I can attest that it isn't totally snake oil.