One overlooked used car warranty feature is emissions control coverage. This is usually an optional coverage in an after market auto warranty, but given today's tougher emissions standards it is a worthwhile expense. 

Your individual coverage may vary, but used car warranties connected with emission control usually pays for repairs including your fuel sensor, fuel tank pressure control valve, thermal vacuum switch and other parts affecting your car's emissions. This used car warranty only covers the repairs of these individual parts of your emissions system, and does not guarantee you will pass an emissions test. 

There are a many factors that can affect your vehicle's emissions, your mechanic can advise you on the right combination of repairs and routine maintenance that will help your vehicle stay in compliance with the laws governing vehicle emissions.