How to encourage Chinchilla to eat more hay?

I adopted a Chinchilla about a month ago, and he definitely has a preference for pellets over hay (probably how he got his molar spurs which had to be removed a few weeks ago).

How do I get him more interested in hay? I now have several varieties of it, but he still has a preference for pellets. I can cut the amount of pellets available but I don't want him to go hungry... I've tried stuffing the hay into a jar of oats to have them smell like oats, because he loooves oats, but he wouldn't...

How to encourage Chinchilla to eat more hay?