Etiquette on contacting past owner of your new RV

I have contacted a previous car owner to ask what oil he used. He was happy to here from me and was glad to hear the car found a loving home.
However, he couldn't answer my question because it was a lease and he always took it to Infiniti for service.

On the other side, I sold a TT to a couple who have called back to ask 'how to' and 'did you' questions. I was happy to hear from them and glad they are enjoying their new toy.

YMMV