My shifting was getting a little sloppy plus the chain was making a lot of rattling noises on my recumbent. I checked it with my wear gage tool:
Mine was worn past the 0.75 line so was way overdue for changing. It is also recommended that you change out the rear cassette when you change the chain, so I finally got around to doing this. The downside is that on a recumbent you actually have to buy three chains and hook them together to get a long enough chain, so it’s a bit pricier. The upside is that the chain lasts longer because each link passes over the gear teeth less often. It was still pretty inexpensive (less than US $100) to order all this on Amazon. A local bike shop will also do this for you for a reasonable price.
What a difference this made! I knew there is evidence that a worn-out chain can waste about 5% of your power, but it feels like more than that. Now I seem to fly along considerably faster, at least 1 mph, with the same effort. I enjoyed this feeling a great deal on my recent tour to the Southeast of Morgan Hill.