Hi, I'm new. Someone from the CivicX forum recommended I join here. My 2017 Civic Si Sedan is mostly stock. PRL Stg1 intake pipe, drop in dry washable filter, TSP Stg 1 with ktuner. I typically run map 3. According to the tripmeter built into the car by Honda, I've averaged 42-47 mpg. But the math always seems a little off. I generally run the tank down to nearly empty before filling up, it's a 12.3 gallon tank per Honda. My fill ups range between 10.3 and 11.7 gallons. Most tanks I see between 470 and 510 miles per tank. My driving is about 80 highway, mostly alone with just my work equipment and dad stuff (car seats, stroller, etc) in the car.
My driving style is roughly living between 1-2k rpms, and avoiding boost unless I need/want it. When I use boost, I pretty much downshift and stand on it for only as long as needed, then shift back into an overdriven gear. I am not a fan of coasting out of gear. I stay in gear and downshift to decelerate while applying the brakes very lightly unless more is needed. I do this more as a courtesy to people driving behind me than for the actual braking effort. As a result, I've got over 30k miles on the stock clutch, tires, and brakes and all of them look to be good for another year. I'm in NJ, where Winter can randomly dump a crap of sleet and black ice on us. The stock A/S tires are not great in the slippery stuff, but I've been driving manuals long enough to generally handle it well enough to be safe.
Previous cars are a 300whp 2002 WRX (many boltons), 480hp 2002 Z06 (intake, ECS tune), 450whp 2011 EVO-X (many boltons), and a couple n18 based mini Cooper S with just the BurgerTuning JB+ piggyback.
So, that's pretty much my introduction. Hope to learn from others and share my experiences.