Everyone’s not is better than mine.
 

I just joined here but have referenced this site for years. My averages are always lower. My current vehicles best long distance highway trip is worse than some people daily average. I don’t drive aggressive or anything. If I try really hard( no ac, shutting engine offf etc) I can get my average on a tank up but it’s still lower than most people. Even my current the dash indicated long term when I bought it was about 50% better than I get now and still better than my best tank ever. Even at 55 downhill with a tailwind I don’t average these numbers lol. I’ve used a live data tool and my o2s seem to be working good so idk.

What year, make, model, trim level, transmission, tires, modifications? All those can affect overall. More info may help with ideas and suggestions.