Cannondale has been maintaining our 20KW Generac Guardian Series generator (first installed in 2012) for 2 years now. During the recent power outage, the generator ran flawlessly for 130 hours straight. We added 16 ounces of motor oil after the first 75 hours of run time, as would be expected during a period of extended usage. The professionals at Cannondale were reachable, and provided helpful advice on lubricant selection, among other things. If you own a generator and live in Westchester or Fairfield counties, you must become a Cannondale client. They are the absolute best!