When I try to give a group the permission to spawn the mini with unlimited fuel, I get this:

10/10 20:21:57 | Permission 'spawnmini.unlimitedfuel' doesn't exist

That shouldn't be possible. Are you sure the plugin is loaded? Can you run o.reload SpawnMini and paste the output here?

Sorry, I was on the wrong site, but I'm glad I found this one.. it might be better. 

Merged post

Ok, this one works as expected. There's a plugin that uses the same commands on another site and I forgot where I had gotten that plugin but I'm glad I got this one. It works better.