I had the same thing happen to me with my new-to-me TS1610F. I was concerned to say the least. But I drained it all out and added back in 30W oil (as indicated in my manual). After much use I check it now and then and I still see no diesel dilution in it. So I think you will probably be fine. Just check it occasionally and if you have to change it now and then not a big deal as long as it runs fine. I ran mine a few hours when I got it before I changed the injector pump oil and it seemed to run fine, so there is apparently sufficient lubricating qualities in the diesel to substitute for motor oil for a while at least.
Bill