Recently i got a civic hybrid. At first I got like 25 mpg. I changed the engine oil, CVT fluid, all the filters, tires have the right pressure and what really helped, i cleaned the maf sensor. I'm getting 31mpg now but its still pretty low. The car has 75k miles on it and a pretty fresh ima battery from 2015 and it drove like 22k miles since then. So what else can I check for better mpg? I'm thinking about spark plugs and serpentine belt.

Spark plugs wouldn’t hurt, serpentine belt shouldn’t make any difference. It’s also dependent on how you drive. 31 mixed is low but not horrendously low.

I really try to get as much mpg as possible when i drive