Understanding Diesel Exhaust After-treatment Solutions

With Tier 4 Final emissions standards in place, the use of diesel exhaust fluid (DEF) is required for diesel engines over 74 hp. As part of the selective catalytic reduction (SCR) system, DEF has been used in over-the-road trucks and other construction equipment for years. Equipment that doesn’t require DEF, like some of our JLG® and SkyTrak® telehandlers, use a diesel oxidation catalyst (DOC) system. So what’s the difference between all of these acronyms, and how does it impact you?

What is Selective Catalytic Reduction (SCR)?

SCR is an advanced active emissions control technology system that injects a liquid-reductant agent (DEF) through a special catalyst into the exhaust stream of a diesel engine. Particulate matter and other exhaust emissions will oxidize and burn off in the catalytic process, so the exhaust comes out cleaner. Under normal use, the SCR system doesn’t require any user interaction when in use and there’s no maintenance other than keeping the DEF fluid full.

Telehandlers with engines over 74 hp use an SCR system that requires DEF. JLG considered end user applications, as well as owning and operating costs and reliability in the field, when choosing SCR and DEF for Tier 4 compliance.

What is a Diesel Oxidation Catalyst (DOC)?

Select JLG and SkyTrak telehandlers come standard with 74 hp engines that use DOC to achieve Tier 4 Final EPA exhaust emissions regulations.

A DOC is a device that utilizes a chemical process in order to break down pollutants from a diesel engine in the exhaust stream, turning them into less harmful components — similar to a car’s catalytic converter. DOC technology doesn’t require DEF and therefore eliminates the cost of the DEF and having to worry about keeping the tank full.

JLG Diesel Engine Options

JLG offers engine options for its JLG and SkyTrak lines of telehandlers to meet varying application requirements.

SkyTrak 6036 and SkyTrak 6042

74 hp engine is standard
The 74 hp engine meets the majority of end user applications

SkyTrak 8042, SkyTrak 10042 and SkyTrak 10054

110 hp engine is standard
The 110 hp engine is designed to meet all end user terrainability and performance needs in a wide variety of applications
Those operating on firm, level surfaces at lower elevations will likely find the optional 74 hp engine adequate for their needs

JLG 742

74 hp engine is standard
The 74 hp engine meets the majority of end user applications
Those operating in challenging, rough terrain or at higher elevations with likely prefer the optional 110 hp engine

JLG 943

110 hp engine is standard
The 110 hp engine is suitable for the majority of end user applications
Those operating on firm, level surfaces at lower elevations will likely find the optional 74 hp engine adequate for their needs


Whatever your application, you can trust that JLG will provide equipment solutions that meet changing Tier 4 regulations and emissions standards while also providing you with the options you need to get the job done.