The Nebraska Tractor Test Lab’s Roger Hoy offers this list of questions to consider when buying your next 174-plus-hp tractor:

Selective Catalytic Reduction (SCR) systems

1 How much diesel exhaust fluid (DEF) is required?

2 What is the cost of DEF? (This number varies significantly when you compare buying the jugs that contain several gallons with buying in bulk.)

3 Will I need an additional pump and tank to store DEF and possibly an additional supplier?

4 Because DEF is a consumable fluid, how can I compare the total consumable fluid cost of a SCR system to both a Tier 3 system and a diesel particulate filter (DPF) system for various farming operations?

5 If I choose an EGR/DPF system now, will I have to deal with DEF anyway when final Tier 4 is introduced in 2014?

Exhaust Gas Recirculation (EGR) systems

1 How often will active regeneration occur in various farming operations?

2 How much incremental diesel fuel will be expended in active regeneration?

3 Can I continue using the tractor as I like during an active regeneration or will productive farming operations be affected during regenerations?

4 How can I compare diesel fuel costs to traditional Tier 3 systems and the SCR systems that use both diesel and DEF?

5 If I choose a DEF system now, will I have to deal with a DPF system anyway when Final Tier 4 is introduced?