> My assumption are farmers are trying to skirt the eco rules for vehicles in some way.

They're using remanufactured 90s cummins for this reason. They're pre-DEF. Modern regulations have killed the diesel engine as a reliable workhorse. It's easy to write off the woes of this segment as corporate greed, but we've made it illegal to build a simple reliable tractor like this.

> The Kubota M5-111 is a 105.6 HP utility tractor that uses Diesel Exhaust Fluid (DEF) to meet Tier 4 emission standards, with common issues including Code 202A, DEF sensor failures, and clogged injectors. The system includes a dedicated tank and filter (Part #1J508-19660). Owners often report issues with the DEF system causing power derates, leading some to consider deletion or repair, though these issues can cause significant downtime