coal roll

“Coal roll” is modifying a diesel so it belches black smoke on demand—fuel turned into soot and applause from exactly no one.

In Australia it’s illegal: tampering with emissions gear breaches ADRs and state laws, and can earn defect notices and hefty fines.

It also wrecks air quality, irritates everyone behind you, and usually signals a bad tune rather than any real performance gain.

If your diesel’s smoking like a bushfire, it needs maintenance—think filters, injectors, and a proper tune from a reputable shop.

Short version: don’t do it; keep it roadworthy and enjoy torque without the smokescreen.