Far as DEF, EGR and DPF is concerned, you don't need to look much farther than Class 8 diesel trucks to see the issues related to and as far as the previous statement that they are more efficient, thats pure BS. I know, I work at a truck dealership and they (Tier 4 final on road diesel engines) are problematic, inefficient and failure prone. Same applies to tractors that share the same components from the same manufacturers. Here is a scenario, you tell me what you'd prefer, a ECM controlled Tier 4 compliant engine or a mechanically injected pre Tier 3 engine. I think the 'educated' choice is clear..... You only have one tractor a Tier 4 final compliant Kubota (for the sake of a brand only), it's a Sunday and you are 3/4 of the way done round bailing first cut alfalfa and th NWS says there is a 60% chance of heavy rain that evening. The sky is turning darker with storm clouds and all of a sudden your check engine light comes on. The tractor derates in power (thats exactly what occurs when the ECM detects an error code has been registered in the computer memory). You are now developing much less PTO power than the round bailer requires to make a bale and rain is eminent. Keep in mind, it's Sunday afternoon so no dealer is open, not that it matters because the only way for the dealer to diagnose the fault code is to plug into the Serial Bus and download the fault code into his computer, then he can diagnose the issue and make necessary repairs.... Problem is, it's Sunday, it's about to rain and you are in the middle of a field...... not pretty Think that won't happen? Better think again because it will and more than once. Most of our emissions related problems come in on a wrecker, why? Bcause the engines derate and somtimes completely shut down and many times, all that has occured is a sensor failure. A 20 dollar part made someone have a very bad day..... So tell me, do you want a Tier 4 final tractor or a pre Tier 4 unit, preferably pre Tier 3? I know what I want. I want to see those visible particulates come out the exhaust stack when I give it fuel........:thumbsup::thumbsup::thumbsup: