I bought a 2010 prius used at 163k. When I bought it, I was getting 49+ mpg. Eventually though, it started dropping. Since I bought it, I’ve done all oil changes myself using Mobil 1 oil and have been trying to take good care of it. I have access to most service history and it was taken care of at the shop for mostly everything. Any way, I was kinda curious if fuel injector cleaner could help, so I got some Lucas cleaner and ran a couple bottles of that through separately. I think the first bottle made the mpg drop down about 8-10 miles per gallon, then the second bottle made it drop even more. Yesterday I decided to try that chevron Techron cleaner and I noticed it’s starting to drop more again. Problably 10k miles ago I changed out the spark plugs and decided to go with Ngk iridium’s. At this point I mean I don’t know what to do. Right now I’m sitting around 38mpg.