There are different kinds of saddle soap (consistancy, etc.), so if you rub it on, go very light at first. In any case, you probably ought to test a spot first. Since you are considering saddle soap, I'm guessing that they need a good cleaning. My seats are not hounds tooth (and/or cloth of any form = vinyl), but when I first got the car they were pretty soiled. I used Armour All cleaning wipes and then their seat cleaner/treatment. The cleaning solution does get into the small grooves, but a tooth brush and dry cloth takes care of that. I've also used the cleaning cloths on the metal dash parts, etc. I just went easy at first. Meguiars and others also make seat cleaner.
I've used saddle soap on everything from car seats to ball gloves, if you use it: test and go lightly at first.
(OK, what John says below is obviously right! But you did say "vinyl", so I assumed you did not mean the actual hounds tooth "cloth" --as I said above. I'm not sure where you are from, but I've never seen "Vinylex" on the shelf. I did have it highly recommended to me a few years back, and even though its parent company, Summit, was located only about fifty miles away, I could never find it. I do know you can order it through NPD and some other places. And after seeing that picture of John's Vette, I think I'll order some... Good luck!)