Awesome
oh, and a trick for getting more gas into your tank when you fill up is that when you know you're getting close to full, back off the trigger on the gas pump and put the gas in slowly. This will let you fill up the tank more than you already do because the pump won't click so early. The sloshing around of gas while filling up at full pace causes the pump to prematurely click. This won't do anything for gas mileage, but you'll squeeze a little more miles out of a tank of gas.

 

you should do what trust does the whole time though. when you pump in gas fast, the gas from the nozzle hitting the gas already in the tank, the splash causes gas vapor to be released more rapidly, and with the nozzles gas return section, all that vapor goes right back into the pump. if you're barely on the nozzle the whole time, the gas basically dribbles down the side of the tank, causing much less splashing.

think of it as pouring a beer into a glass quickly and having it foam up and overflowing, or pouring it slowly down the side and getting little to no bubbles

 

I live in CDN we had a brutally cold winter, my civic usually fills up for 51$ and I could get about 525-550km on a tank, on the last 3 fill ups I have been getting about 400km. I'm not sure if it's due to cold outside temperatures, I should be able to know this week

I put in a bottle of injector cleaner, I toped the air up in the tires I purchased a new air filter (didn’t install it yet)

There is no engine light on, the power seems normal (thought maybe a spark plug was bad) On the net someone posted this


It could be a number of things. A bad oxygen sensor will cause poor fuel economy. Is the check engine light on? If so have it scanned and follow the codes they give you. A dirty mass air flow sensor can cause this. You can inspect it and clean it with a special cleaner available at most auto parts stores. A faulty coolant temperature sensor will also cause poor fuel economy. A dirty air filter will also cause poor fuel economy. Check for vacuum leaks, a vacuum leak can tell the ECU to richen the air/fuel mixture to compensate for a vacuum leak.

Do you think any of the above mentioned could occur WITHOUT flagging the Engine light? Not sure how to approach this,

 

your primary oxygen sensor is your air/fuel sensor. a dirty primary oxygen sensor should be replaced every 60,000 miles but no it wouldn't cause a check engine light if dirty. winter gas has additives that cause worse mpg because of the cold air. i would suggests you do a basic tune up air filter,oil,plugs then go from there.

 

if you want to check for leaks try this.
How To Find A Vacuum Leak - EricTheCarGuy - YouTube