Engines will play a key role in tractor-buying decisions in 2011. That’s because on January 1, all off-road diesel engines rated 174 hp and higher must comply with the Environmental Protection Agency’s Tier 4i (interim) emissions regulations. These rules will affect high-horsepower tractors, combines, sprayers and other self-propelled vehicles used in farming.

The EPA has been regulating diesel emissions on farms since 1996. This latest round of cuts calls for a 90% reduction of particulate matter (PM), also known as soot, and a 50% drop in oxides of nitrogen, or NOx, the stuff that forms smog, in relation to Tier 3. How clean is that, you ask?

“With the new Tier 4A engines, the air coming out of the engine is so clean you can hardly see any exhaust,” says Tom Dean, marketing manager for Case IH high-horsepower tractors.

The end result is cleaner air and a healthier environment. But clean air comes at a price, which can vary according to the technology being used, making it pay to do your homework.

“Tier 4i engine technology will add anywhere from 4 to 9% to the price of a 2011 model tractor,” says Dave Kanicki, executive editor of Farm Equipment.