The average diesel injector will last between 100,000 and 150,000 miles. The key is to try and get them all as close to the 150,000-mile mark as possible. This is where injector cleaners come in. If you use an injector cleaner consistently throughout the life of the injectors, there's a good chance you'll be able to get the full 150,000 miles or more out of them! Considering each injector costs about $45 and many diesel engines have eight of them – that's $350 to $400 in parts alone! Once you add in labor, it can quickly turn into a $600 to $700 job. Getting your injectors to last that much longer pays for the additives themselves, and fuel efficiency savings are just an additional perk.