Plugin Abuse

Is there a way to set up the plugin so only mounted vehicles get fuel / repairs? Or at the very least, a way to blacklist certain individuals from being able to use the feature? Too many players are abusing the plugin on my server. The intended purpose is for them to fuel up, repair, and go. But I have consistently been catching players pushing vehicles into the zone to farm the free fuel. I would like to prevent this, if possible, without kicking or banning them. Please advise.