The Environment and Engine Design!
Engine emissions are the top issue with lawn equipment and are primarily caused by incomplete (in-efficient) burning of fuel and fuel additives. Two primary reasons for an efficient or in-efficient engine include; 1) engine design and 2) engine condition. Regarding Design; some engines are more efficient and less polluting due to their design. "Air index" tags, required by the EPA on all new engines, identify the "greener" mowers. The air index shows the polluting measure of that engine on a scale of 0 to 10 relative to other engines in its class. 0 is the best and 10 the worst. By 2011, a new "phase" of EPA regulations will be in place holding the manufacturers to even stricter standards. You will see a variety of design changes soon to begin meeting the new codes. For now, watch for the "Air Index" tags to find the lowest polluting engine options when buying new equipment.